What is your RAM? If its at 4 or 6 GB then anything above huge will be disabled.

I should probably note that I was able to play insane maps in multiplayer up to beta 6.2. After that the note was that "Map sizes above huge have been disabled in multiplayer"

Multiplayer is undergoing stability QA.  There were some issues with MP that cropped up late in the beta, so Stardock shut down everything that was buggy and they are turning them back on one by one.  I think I heard them say in devchat today that multiplayer should be fully functional within a week or so.  Unfortunately, QA testing on insane maps takes a lot of Stardock people hours.