Large model converted to proxies won't open, but will merge into new max file.

[Noah45]

Had to keep my project opened on the computer because, if it crashed, the file would not re-open. The only way to have access to my model was by merging into a new max file.
The apparel in this retail store prototype was getting massive, so I converted them into several groups of proxies. It was after the conversions, the file would not open- directly.

Strangely, it would open in Max2017, but I'm using Max 2016.

Would have guessed it's Max thing, but proxies are involved.