Script Execution Order no longer lists scripts and can't be altered.

I'm using Unity 5.4.4. I've attached a screen shot someone else made a while back that perfectly demonstrates this problem.


How can I get my Script Execution Order back? My project is many gigs and years in the making.

Other projects display the Script Execution Order properly with the same Unity version so it's something related to the project itself. No errors displayed. No idea.