For some Reason the (epic) Viking Helmet of mine as well as the (epic) leggings wont upgrade further with the epic upgrades even though they have still upgrade points available (3 and 1 points). Currently playing on the Isslkalian Foolpackserver Herkules.

Same here

I can second this issue. We have the same problem on version 1.12.2-0.2.30.jar

1.5 years later, and can verify this same bug is affecting me as well with all four pieces of armor I'm currently wearing

Sooo.... I think I figured it out with some testing... I am pretty sure each (singular, not level of) enchantments, as well as each Attribute modification from Quality Toots, counts towards that total. I am not sure if the coding restricts the number of upgrades by the numbers of lines of code allowed on the item, but that is my guess. Ideally, you want to upgrade your items first, then modify the attributes/enchant. Hope this helps. Sorry I am 2 years late lol.