I can't complete, Execute Anonymous Blocks Challenge

I made Custom Object name is Candidate.

Can't edit Plural Label in Playground. Is right?


I clicked 'Verify Step'
and...     Challenge Not yet complete... here's what's wrong: 
Could not find an object with Plural Label Candidates.




Then I changed Singular Label : Candidates.
and : 
There was an unhandled exception. Please reference ID: TPOJWISC. Error: Faraday::ResourceNotFound. Message: NOT_FOUND: The requested resource does not exist


Okay, Then...
I made Candidate, and Candidates. Two Custom Object...
and : Challenge Not yet complete... here's what's wrong: 
Could not find an object with Plural Label Candidates.


What happen....?
How can I complete this unit?


Please need your help.....
I'm not complete simple challenge...