I assume its probably the same incompatibility issue most custom huds will have, but despite being very similar to the vanilla hud the thirst meter doesn't render with Armor Points ++ installed. I'll drop a mention of the issue on their page as well.

Thank you for your time.

https://www.curseforge.com/minecraft/mc-mods/armorpoints

After searching Armor Points ++ issue page I found a reply the mod author wrote ... hopefully it'll be helpful.

The way Armorpoints++ works on fabric is by replacing the Gui class - most mods that use mixins to inject themselves into any methods of the vanilla gui class won't work with this approach, while all mods using the fabric api event will still work. If you want, I'll mark this as a feature request for specifically adding support for better mount hud and dehydration.

is there a way to hotfix it manually in the mean time ? i have a lot of knowledge about programming as it is my job. Tho i don't know shit about minecraft moding, i should be able to do something if i know where the problem is

No I don't think so but I am open for a PR.