No idea what's happened here, but I downloaded the mod, put it in my mods folder, logged in (Forge: 28.0.45, Minecraft: 1.14.4, mod version: ElevatorMod-1.14.4-1.3.11) and I opened the inventory, scrolled to the blank tab and... yeah. Sorry. Not sure what other information you need.

I currently have the following mods:

eta: I don't think this is an issue with your mod, but Forge or myself, because now the same thing has happened to two other mods...
forbidden_arcanus-1.14.4-1.0-Beta-2
stal111/Forbidden-Arcanus#9 (comment)

compressed_items-1.14.4-1.0
stal111/Compressed-Items#2 (comment)

I'm not sure what the issue is... Is one meant to delete config. files when updating a mod?
Sorry to be a bother.

Works fine for me, are there any errors in the logs ?

Uhm I'm not super sure how to check that for you, but stal111 was able to correct Forbidden Arcanus so they might be able to tell you the fix for yours? I can politely ask them if they have any advice if you'd like.

eta: there are a lot of errors in the Latest log but idk which mod they're from.

1.14.4-1.3.11 was compiled with forge 1.14.4 - 28.0.11, maybe it just needs to be recompiled with the new version, try this one (extract jar and install normally)
elevatorid-1.14.4-1.3.12.zip

Sorry... I installed it like normal, but there's no elevator block tab, nor the blocks themselves. But my game is so broken right now I wouldn't be surprised if there was nothing you could do to fix it at the moment.

No problem, can I have a log, just to take a look at?

latest.log
debug.log
2019-08-08-3.log.gz
I hope any of these can help. If you need anything else, please let me know!

I already know compressed items and attained drops are a problem in that list.

Forge .45 has breaking changes and many mods need to recompile for it or it breaks registration of blocks.

Have been fighting with this for over 12 hours now testing one mod at a time.

Can you try 1.14.4-1.5.1 and see if it works ?

Closing unless anyone still has issues.