I am trying to override the tab of a custom object to a Visualforce. I am using a Standard Set Controller in the page. All the documentation I've found said it is possible to override a tab with a Standard Set Controller, but the page doesn't show up in the Visualforce page drop down. Is there something I'm missing as to why it's not showing up?

Visualforce page code:

<apex:page standardController="SVMXC__Installed_Product__c" recordSetVar="installedproducts" extensions="PortalTabRedirectController" action="{!redirect}">
    <apex:enhancedList type="SVMXC__Installed_Product__c" height="700" rowsPerPage="50" customizable="false"/>
</apex:page>

Extension code, in case that's relevant - I purposely wrote it to be not specific to any object, as we are trying to override the tab for multiple objects in the same way. Basically we want the standard tab to show for all users except for our Customer Portal users, who instead will only see the enhancedList just showing all the records, instead of the Recently Viewed list.

public with sharing class PortalTabRedirectController {
    public String keyPrefix;
    
    public PortalTabRedirectController(ApexPages.StandardSetController stsc) {
        SObject obj = stsc.getRecord();
        Schema.SObjectType objType = obj.getSObjectType();
        Schema.DescribeSobjectResult result = objType.getDescribe();
        keyPrefix = result.getKeyPrefix();
        system.debug('Variable keyPrefix: ' + keyPrefix);
    }
    
    public String getKeyPrefix() {
        return keyPrefix;
    }
    
    public void setKeyPrefix(String keyPrefix) {
        this.keyPrefix = keyPrefix;
    }
    
    public PageReference redirect() {
        Profile p = [SELECT Name FROM Profile WHERE Id = :UserInfo.getProfileId()];
        system.debug('Profile Name: ' + p.Name);
        
        String tabURL = '/' + keyPrefix + '/o';
        system.debug('Variable tabURL: ' + tabURL);
        
        if('Customer Portal'.equals(p.Name)) {
            return null;
        } else {
            PageReference pageRef = new PageReference(tabURL);
            pageRef.setRedirect(true);
            return pageRef;
        }
    }
}

 Any thoughts would be greatly appreciated!