Well, that's a relief... I nearly had a mild stroke for a minute there (I had already put GOAL down as my affiliated organization when I sent in my CMP M1 carbine order).
I had nearly the same issue awhile back.
When I had first registered with the CMP, Mass Rifle Association was a participating club and I was able to order a Garand and ammo.
A few months later I ordered more ammo. They processed the order, but sent an email informing me that I'd have to resubmit documentation showing membership in a CMP affiliated organization.
Seems that MRA was no longer a participating club so I had to find an alternative. Fortunately, GOAL was a participant and I was covered once I mailed in a copy of my membership card.