Who is your client, TP, partner, or both, and what state. It is possible to do 1031 exchange on 50% of home, but depends on details. 1031 is only for investment real property

Your taxpayer does need to file  a NJ nonresident return to report the sale of their 1/2. The gain will be taxable. Any withholding in excess of the actual tax will be refunded.

is the partner your client as well? If not, then what they did with that half is irrelevant to you and if it was not an investment property then they shouldn't have been able to do the 1031 exchange, 

What paperwork do you have? 1099-S? and for what amount? The property was sold in NJ so you would do a nonresident nj return for the sale for the gain so the withholding might not be refunded but you still need to file it. 

Is this an existing client or new client? I'd be asking a lot of questions on if this was a second home? Rental property? (was it rented out? What did they do with it for the last 3 years? Being told 1031 sets off a lot of questions for me 

So, your client held the property for 3 yrs. (22>>25). You say he is not a NJ resident. Well, if the house is in NJ, did he live there for 2 years as his primary residence, before he became a Non-NJ person?  That's the only way I could see the sale being a non-taxable event.