Most of my installed plugins aren’t working now due to a strange bug with UI theme being a missing member.
This started when I downloaded and opened the place file contained in this devforum reply. It forced a studio update, closing my open studio windows. When studio had completed updating and opened that place file, I was getting the UI Theme not valid errors/warnings.
I reinstalled roblox from www.roblox.com/download, but no dice. Then I deleted my User/AppData/Local/Roblox directory and did another install, still erroring.
As a backup; the placefile that caused this problem is here. I don’t recommend downloading it and opening it. GameNotWorking.rbxl (31.2 KB)
Sorry for the disruption wrt plugin breakage. We didn’t realize that many existing plugins rely on this - we are going to revert the removal of this property with a Studio patch tomorrow morning. Plugin authors are still encouraged to migrate to the new Theme API but existing plugins should start working again tomorrow.