I've had frequent troubles getting MCE assignments as an AS MVP Gold, however I find that trying a number of different MCE seats usually gets me a seat assignment that actually sticks.

So if say row 8 or 9 don't work on a 738, row 11 does. I've had similar experience on the 77W, for whatever reason I couldn't get a seat in an otherwise open row 16, but was able to get something in row 18. Ditto for the A321T, I can never book the first MCE/exit row even if it's open, but I'll get row 14 or something after a few tries.

There's definitely some sort of glitch, but MVP Golds still have complimentary access to domestic and international MCE.

Trying to contact AA about this, even the usually helpful Twitter team, has been useless for me.