Trying to complete the "Create an approval process that validates when a Prospect Account becomes a Customer."

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.DmlException: Insert failed. First exception on row 0; first error: FIELD_CUSTOM_VALIDATION_EXCEPTION, Account number must be 8 characters long.: [AccountNumber]

 

Hi All, 

I'm trying to complete the Process automation trail -> completeing the task "Automate sets of delayed actions with workflow" I made a couple of errors my first attempt - and deleted the workflow. The problem is I have also deleted the unique identifier that trail head uses to mark the test. Is there any way to get that unique identifier back or resolve this issue to complete the activity? 

thank you in advance, 
Steph 

Trying to complete the "Create an approval process that validates when a Prospect Account becomes a Customer."

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.DmlException: Insert failed. First exception on row 0; first error: FIELD_CUSTOM_VALIDATION_EXCEPTION, Account number must be 8 characters long.: [AccountNumber]