So I've been trying to update a mod (not mine, but for private use) from 1.10.2 to 1.11, and I've managed to resolve all of the error-generating problems, but now I can't figure out why the mod's localization .lang files aren't being parsed and injected.  This is happening both in Eclipse's debug and in an obfuscated runtime environment.  I've debugged the entire process down to the point of seeing that the mod is added to the resource pack, but the lang files are never parsed by the LanguageMap.  I've double checked the file and folder structure a dozen times at least, and it is proper ("assets/{MOD_ID}/lang" from the mod root) in both environments.  In the FMLClientHandler class, under addModAsResource, resourcePackType is not null, and obviously the mod is getting added to the active list and the modNames table (the items and blocks show up in the creative tabs).  Thus, when I load the game, I get tile.{MOD_ID}:{UL_NAME}.name for all of the tooltips over the blocks.  And when I look in the lang file, it's an exact match to whatever block or item may be in question.

 

I am thoroughly lost on this one.  Where can I look next to try to resolve this?

you have to transform all the assets to lower case, including the lang files. (For example: en_US -> en_us)

Indeed, thank you.  Those were the only resources left that hadn't already been converted to all lower case.