Has anyone ever successfully had United "unlock" a travel credit for your use, after cancelling a flight that was booked by a travel agency?

For context, I cancelled a work flight the other day because I was able to take a Frontier flight last-minute using my GoWild pass instead, and when I went to cancel the United flight the website just told me I would receive a credit to use at a later date. It didn't mention anything about it being held for use only by the travel agency.

When I went to go use the credit, though, I get the error message that only the travel agency is able to use the credit.

Wondering if that's a "soft" restriction, and if calling/chatting when I'm ready to book something new will result in them being able to make an exception.