I have performed the steps in my dev org and a playground and continue to get the error message listed below.  I have performed all of the proper steps and nothing should be incorrect.  "Challenge Not yet complete... here's what's wrong:  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: TKTFMGAH"

I have performed the steps in my dev org and a playground and continue to get the error message listed below.  I have performed all of the proper steps and nothing should be incorrect.  "Challenge Not yet complete... here's what's wrong:  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: TKTFMGAH"

Part of the questions asks for the following:

"Change the 'UUID' field on the 'Phone__x' external object to be an indirect lookup relationship to the 'User' standard object. Use the 'Phone_UUID__c' field as the matching key for this indirect lookup relationship."

Every time I create this Indirect Relationship, it just allows me to select the "Accounts" Object, not the User object. Why is this happening? Can anyone help me with this issue?

Thanks!