Hi, I attempted to add the Tough feat to a level 20 character via a homebrew shield, and it's not changing my hit point maximum. Here's the character sheet and the link to the shield.

https://ddb.ac/characters/74635652/wXfbWU

https://www.dndbeyond.com/homebrew/creations/magic-items/5039505-stonewall-legendary/edit

Magic Items aren't able to add Feats, the modifier that does that only works for Races.

You're not attuned to the shield. Did you try that? I ask because it's also not providing the full AC bonus.

Attuned, and still not working. I also tried adding the feat outside normal level progression, didnt work either. Also, I did allow for feats to be used on the home section. 

2 things. 1 you don't seem to have the tough feat.

2 you aren't using fixed HP or your max HP is manually over written, because you have less HP than you should at level 20 even for a full fighter, let alone a barbarian multiclass.

Ah! Thanks!

Thank you all! I was able to get it working once I removed the overwritten HP. Thanks again! 

I'm not seeing the feat added to the character. Are you sure you're using the official feat, not a homebrew version, and added it to the sheet correctly (not through an item, because, as mentioned, that is not yet possible)?

If you , or anyone else reading this, need help adding a feat manually to the character, I made a video.

EDIT:

So I didn't refresh before posting and this all got resolved. I'm just gonna leave this here anyway, in case it helps somebody and y'know, shameless self-promotion. 

I did add the official version. Thank you anyway!