New Mexico return question

[ajp]

A client who lives in New Mexico sold property in Idaho.  It was land used as a farm.  After moving to NM, he was no longer farming so he sold it.  He lived in NM all of 2021.  Property was sold in 2021.  I thought everything was fine, but NM sent him a letter stating that we can't use the deduction for taxes paid for another state because: 

“PIT-1 line 20, Credit for taxes paid to another state disallowed/adjusted.  The income should be allocated on schedule PIT-B.”  

“PIT-1 line 20. A credit is not allowed for tax on income that is not required to be allocated to NM on schedule PIT-B 1, 2, 3, and 7.”

I don't do a lot of NM returns, but I can NOT get the software to let me do anything with PIT-B.  I've downloaded the instructions, but I am missing something.  Why wouldn't the full amount from the sale of that property be on the NM return?  How can I get the software to treat it the way NM wants it treated?  I know I can just have my client send in the extra money, but I want to learn for any potential next time. 

Thank you!