Attributes problem 1.20.1

[BellavistaGiulio]

Hi! I've installed a mod on a hybrid Spigot/Forge server, version 1.20.1, but when I try to assign custom attributes to items, for example, life steal to a weapon, it doesn't seem to recognize the attribute and it's not even displayed in the weapon's "lore". Any possible causes and solutions?
Thank you very much.