We are playing on a 1.12.2 fairly modded server with IV and a couple of addons and for some reason the recipes for the benches aren't showing up on JEI and looking up the recipe doesn't help either

I have a similar issue:

I upgraded to MTS_Official_Pack_V23 just now. However, I realized I can not see recipes with JEI anymore. (I'm using jei_1.12.2-4.16.1.302, and it was working in V19)
I can see the recipes for vehicles, but I cannot see any recipes for decor bench or any other benches.

This is because I removed them for the latest update. Fixed in this commit, 10426f3, and will be fixed in the next update.

Fixed in V21.2.0.

I also cannot see the recipes for the workbenches and cannot find them online.