"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, You can only set a case as escalated if it is high priority and not closed: [IsEscalated]"

Above message is seen when i try to verify my challenge.
Module: Advanced formulas
Unit: Troubleshooting Formula Errors

Solution written for the challenge:

IF( MONTH( TODAY() ) = 12, 
DATE( YEAR( TODAY() ), 12, 31 ), 
DATE( YEAR( TODAY() ), MONTH( TODAY() ) + 1, 1) - 1)

Not able to complete the challenge as "an unexpected error occurs" while verifying the challenge solution. 
Module: Advanced formulas
Unit: Leveling up with Advanced Formulas

Reference error id: BYFMQANQ
 

"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, You can only set a case as escalated if it is high priority and not closed: [IsEscalated]"

Above message is seen when i try to verify my challenge.
Module: Advanced formulas
Unit: Troubleshooting Formula Errors

Solution written for the challenge:

IF( MONTH( TODAY() ) = 12, 
DATE( YEAR( TODAY() ), 12, 31 ), 
DATE( YEAR( TODAY() ), MONTH( TODAY() ) + 1, 1) - 1)

Not able to complete the challenge as "an unexpected error occurs" while verifying the challenge solution. 
Module: Advanced formulas
Unit: Leveling up with Advanced Formulas

Reference error id: BYFMQANQ