Hi all, Why <apex:commandButton> in visualforce page not calling method in controller.

This is code in visualforce page.
<apex:pageBlockTable value="{!addCoach}" var="addC" id="table" style="width:500px">
                <apex:column headerValue="Other Name">
                    <apex:inputField value="{!addC.ServiceName__c}" html-placeholder="Other Name"/>
                </apex:column>
                
                <apex:column headerValue="Currency" style="width:50px">
                        <apex:outputPanel layout="block" styleClass="requiredInput">
                            <apex:outputpanel layout="block" styleClass="requiredBlock"/> 
                            <apex:selectList value="{!addC.CurrencyIsoCode}" size="1" multiselect="false" required="true">
                                <apex:selectOption itemValue="" itemlabel="==Not Specify=="></apex:selectOption>
                                <apex:selectOptions value="{!MyCurrencyIso}"/>
                            </apex:selectList>
                        </apex:outputPanel>
                </apex:column>
                
                <apex:column headerValue="Total Cost">
                    <apex:inputText value="{!addC.Total_Cost__c}" html-placeholder="Total Coast"/>
                </apex:column>
                
                <apex:column >
                    <apex:commandButton value="Add Row" action="{!addRow}"/>
                </apex:column>
                
            </apex:pageBlockTable>

And this code in controller.
public with sharing class CostCalculationExtention{

public List<Product_Service__c> addCoach {get; set;}
//-- Constructor --\\
    public CostCalculationExtention(ApexPages.StandardController controller) {
        //-- Add Coach --\\
        addCoach = [select ServiceName__c, Total_Cost__c, CurrencyIsoCode from Product_Service__c where Id =: productId];
        addCoach.add(new Product_Service__c(Product__c = productId, Service__c = service.Id, ServiceName__c = '', CurrencyIsoCode = '',        
        Total_Cost__c = 0));
        //-- Add Coach --\\
    }
//-- Add Coach --\\
    public void addRow(){
        system.debug('Start Add Coach');
        addCoach.add(new Product_Service__c());
        system.debug('End Add Coach');
    }
//-- Add Coach --\\

}

Thank you in advance