Mod not visible for testing in custom games after build

After a while of working on this without any complications (a long cycle of editing xml, saving, building, testing, repeat), I've decided to rebuild my mod and test out my latest features just like I've always done. However, the mod ceases to show up in the custom game options or even during workshop management. I double checked that it built correctly and in the right place and everything, restarted the tools, cleaned, rebuilt, restarted steam, etc. Tried deleting the .sga from the local mods folder and rebuilding. Nothing. None of those seemed to work. It's worth mentioning the last thing I added is a set of custom portraits, although from what I can discern I didn't make any mistakes in the process of adding them. Templates>Icons, selected appropriate folder, set portrait_name_summer/winter to ModIcons_[modID]_[filename without extension]. However, it's also worth mentioning that undoing said icon changes did not bring the mod's visibility back, either.

I'm dumbfounded and I don't know what else to do other than start a new file from scratch. There's a fair bit of progress on it and I'd rather not start over. I can still edit the xml and what not just fine, but I have no way of testing it to see if it works or not. And if it doesn't even show up for testing, why would it be playable when I publish it? If anybody could lend me some foresight into this issue, any help is greatly appreciated.