I was solving this challenge and my VF code is:

<apex:page standardController="Account" recordSetVar="Accounts" >
    <apex:pageblock>
        <apex:repeat var="a" value="{!Accounts}" rendered="true"  id="account_list">
            <li>
                <apex:outputLink value="https://ap1.salesforce.com/{!a.ID}" >
                    <apex:outputText value="{!a.Name}"/>
                </apex:outputLink>
            </li>
        </apex:repeat>
    </apex:pageblock>
</apex:page>

I am getting the list of accounts as required and on clicking on any of the accouts, it redirects to that accounts detail page.
Still I am getting following error from trailhead:

"The page does not bind to the record ID value (in order to link to the record detail page)"

I'm getting the error "The outputLink component is not binding to the ID of a case" for this challenge. I've checked several threads on here and I'm almost certain it should be correct. It does link to the details page for the case. 

I initially just had the ID linking but have changed it so both case number and id link via id in case that mattered. 

I've also previously tried having a complete url as the value but no luck. 

Any help would be appreciated.

<apex:page controller="NewCaseListController">
 
        <apex:pageBlock title="New Case List" id="cases_list">
            
    <apex:repeat value="{! newcases }" var="cases">
       
        <apex:outputLink value="/{! cases.id}">
        ID:  {! cases.id }
        </apex:outputLink><br/>
        <apex:outputLink value="/{! cases.id}">
        Case Number:  {! cases.CaseNumber }
        </apex:outputLink><br/>    
    
    </apex:repeat>
            
        </apex:pageBlock>