We are aware of a matchmaking issue with the brand new ProAM mode in NBA 2K16. This is going to need a patch update to be fully resolved and we’re in the process of testing this update.
To repeat: This will be resolved in the upcoming patch update. Stay tuned for more news on when it will be released (which could take up to a couple weeks).
In the meantime, there is a simple workaround. Please refrain from quitting while in the locker room before a match-up as that causes the issue. Spread the word to your fellow 2K ProAM players as well.
Thank you for your patience.