Doing CPQ module which is pure configuration. Have tried multiple brand new CPQ orgs without any ad-hoc customisation.  I have attached the error message below. 

Note that, the reference error id kepts on switching.

"There was an unexpected error while verifying this challenge. Usually this is due to some pre-existing configuration or code in the challenge Org. We recommend using a new Developer Edition (DE) to check this challenge. If you're using a new DE and seeing this error, please post to the developer forums and reference error id: XNZOPHSU"

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)"