I too am getting errors and cannot proceed. I end up getting this error message: "Challenge Not yet complete... here's what's wrong:
There was an unexpected error in your org which is preventing this assessment check from completing: System.StringException: Unrecognized base64 character: {"
I had done earlier modules with custom code so I figured removing those components/controller would help, plus, I tried switching out the email addresses in the Custom Settings for the Einstein Package - neither worked.
I'm Bummed! I was liking the Cat Rescue module! :( Hopefully Salesforce can figure out what's the blocker here.

Challenge Not yet complete... here's what's wrong: 'Activate Temp Access Flow' lightning app page doesn't exist with the flow component called 'Accounts Temp Access'. Check the instructions.

Has anyone passed this challenge? I have passed all prior challenges. It seems pretty straightforward, I have my Lightning app page, activated it, added it to Sales...everything else is setup and has passed.