I followed moggy's guide, but I'm facing the error message of "You are not authorized to view this page. The transaction has not been processed."

Can anyone kindly advise where I went wrong in my code?

<apex:page id="CSPayment" showHeader="false" controller="CyberSourcePaymentController" title="Application Payment">
    <apex:define name="header">
        <center>
            <apex:form id="theInput" >
                <apex:panelGrid columns="2" style="margin-top:1em;">
                    <apex:outputLabel value="Amount" for="amount"/>
                    <apex:inputText required="true" id="amount" value="{!amount}" disabled="{!enabled==false}"/>
                    <apex:outputLabel value="Currency" for="curren"/>
                    <apex:inputText required="true" id="curren" value="{!curren}" disabled="{!enabled==false}"/>           
                </apex:panelGrid> 
                <apex:outputPanel id="testout" rendered="{!enabled==true}">
                    <apex:outputText value="{!enabled}"/>
                    <apex:panelGrid columns="1" style="margin-top:2em;">
                        <apex:commandButton id="visa" image="/img/icon/cash16.png" action="{!visa}" disabled="{!enabled==false}" />
                    </apex:panelGrid> 
                </apex:outputPanel>  
            </apex:form>
        </center>
    </apex:define>
    <apex:outputPanel id="testcard" rendered="{!enabled==false}">
        <apex:define name="body" >  
            <center>
                <form id="theForm" action="{!endp}" method="post">
                    <apex:panelGrid columns="1" style="margin-top:1em;">
                        <apex:image id="visa" value="/img/icon/cash16.png"/>
                        <div>
                            <apex:outputText escape="false" value="{!ParametersValues}"/>
                        </div>
                        <!--<apex:outputText escape="false" value="{!ParametersValuesHidden}"/>-->
                        <apex:outputText escape="false" value="{!SignedData}"/>
                    </apex:panelGrid>
                    <apex:panelGrid columns="2" style="margin-top:1em;">
                        <input type="hidden" name="card_type" value="{!card_type}"/>
                        <span>Card Number     :</span><input type="text" name="card_number"/><br/>
                        <span>Card Expiry Date:</span><input type="text" name="card_expiry_date"/><span> format MM-YYYY</span><br/>
                        <input type="submit" id="submit" value="Confirm "/>  
                    </apex:panelGrid> 
                    <br/>
                </form>
            </center>
        </apex:define>
    </apex:outputPanel>
</apex:page>

public with sharing class CyberSourcePaymentController {
    
    private Map<String,String> oPassedParams = new Map<String,String>();
    
    private String access_key = getHOLO();
    private String transaction_uuid = getUUID();
    private String signed_field_names = 'access_key,profile_id,transaction_uuid,signed_field_names,unsigned_field_names,signed_date_time,locale,transaction_type,reference_number,amount,currency,payment_method';
    private String signed_date_time = getUTCDateTime();
    private String locale = 'en';
    public String transaction_type {get;private set;} //either sale or sale,create_payment_token
    private String reference_number = UserInfo.getUserId();
    public String amount {get;set;}
    public String curren {get;set;}
    public String payment_method {get;set;}
    public String card_type {get;set;}
    public String card_number {get;set;}
    public String card_expiry_date {get;private set;}
    private Boolean enabled = true;
    private String ccSelection;
    
    public static String sign(Map<String, String> paramsArray)  {
        String result = sign(buildDataToSign(paramsArray), CyberSourcePaymentController.recover());
        return result;
    }
    
    public String getUTCDateTime(){
        DateTime oUTSDateTime = System.now();
        String strUTCDateTime = oUTSDateTime.format('yyyy-MM-dd\'T\'HH:mm:ss\'Z\'');
        return strUTCDateTime;
    }
    
    public String getHOLO() {
        return CyberSource__c.getValues('testcenter').AccessKey__c;
    }
    
    public String getHOLO1() {
        return CyberSource__c.getValues('testcenter').ProfileId__c;
    }
    
    public String getParametersValues() {
        String result = '';
        
        for(String oKey : oPassedParams.keySet()) { 
            result += '<div>';
            result += '<input type="hidden" id="' + oKey + '" name="' + oKey + '" value="' + oPassedParams.get(oKey) + '"/>';
            result += '</div>';
        }
        return result;
    }
    
    /*public String getParametersValuesHidden() {
        String result = '';
        for(String oKey : oPassedParams.keySet()) { 
            result += '<input type="hidden" id="' + oKey + '" name="' + oKey + '" value="' + oPassedParams.get(oKey) + '"/>';
        }
        return result;
    }*/
    
    public String getSignedData() {
        String result = '';
        result += '<input type="hidden" id="signature" name="signature" value="' + CyberSourcePaymentController.sign(oPassedParams) + '"/>';
        return result;
    }
    
    public String getEndp() {
        return 'https://testsecureacceptance.cybersource.com/pay';
    }
    
    private void popParams() {
        oPassedParams.put('access_key',getHOLO());
        oPassedParams.put('profile_id',getHOLO1());
        oPassedParams.put('transaction_uuid',getUUID());
        oPassedParams.put('signed_field_names','access_key,profile_id,transaction_uuid,signed_field_names,unsigned_field_names,' +
                          'signed_date_time,locale,transaction_type,reference_number,amount,currency,payment_method');
        oPassedParams.put('unsigned_field_names','card_type,card_number,card_expiry_date'); 
        oPassedParams.put('signed_date_time',getUTCDateTime());
        oPassedParams.put('locale','en');
        oPassedParams.put('transaction_type','sale,create_payment_token');
        oPassedParams.put('reference_number',reference_number);
        oPassedParams.put('amount',amount);
        oPassedParams.put('currency',curren);  
        oPassedParams.put('payment_method',payment_method);     
    }
    
    private static String recover() {
        return CyberSource__c.getValues('testcenter').SecKey1__c + CyberSource__c.getValues('testcenter').SecKey2__c;
    }
    
    private static String commaSeparate(List<String> dataToSign) {
        String result = '';
        for(String str : dataToSign) {
            result += (result==''?'':',') + str;
        }
        return result;                         
    }
    
    private static String buildDataToSign(Map<String,String> paramsArray) {
        String[] signedFieldNames = paramsArray.get('signed_field_names').split(',');
        List<String> dataToSign = new List<String>();
        
        for(String oSignedFieldName : signedFieldNames) {
            dataToSign.add(oSignedFieldName + '=' + paramsArray.get(oSignedFieldName));
        }
        return commaSeparate(dataToSign);
    }
    
    private static String sign(String data, String secretKey) {
        String result = EncodingUtil.base64Encode(Crypto.generateMac('hmacSHA256', Blob.valueOf(data), Blob.valueOf(secretKey)));
        return result;
    }
    
    public String getUUID() {
        Blob b = Crypto.generateAesKey(128);
        String h = EncodingUtil.convertToHex(b);
        String guid = h.substring(0,8) + '-' + h.substring(8,12) + '-' + h.substring(12,16) + '-' + h.substring(16,20) + '-' + h.substring(20);        
        return guid;
    }

    public PageReference visa() {
        enabled = false;
        payment_method = 'card';
        card_type = '001';
        popParams();
        return null;
    }
    
    public Boolean getEnabled() {
        return enabled;
    }
}