I'm sorry if this has been mentioned before, I tried a search but didn't see it. I added this to what is technically the Direwolf20 1.16 pack but since it's not on the CurseForge app and only on the FTB app, I found all the mods and just created the mod pack on Curse...
I know the mod is designed for 1.16.5 but I have other mods that are for 1.16.5 that work on 1.16.4 so this isn't really I want this fixed as much as it's just informing you that the mod is a valid mod, just not working...

Stock it was set to STANDING, I changed it to CROUCHING, no go...
Tried KEYBINDING, no go...
Tried deleting the config file to refresh, no go...

Did you make sure the tool was enchanted with Vein Mining when you tested it?

I didn't realize this was not the typical Veinminer by Portablejim that I use... Sorry, yes, I was not using the enchant...