This may sound silly but are you sure you weren't using weapon ultimates? You need to have corresponding weapon equipped in order to use a weapon ulti(e.g. you can't use destro staff ulti while having 2h sword equipped, even though it will let you slot it and will accumulate ultimate points).
If you mean actual class ultimates then yeah that's odd. Never happened to me I think.
that might be it, due to those weapon skills. i was for 2-handed until i maxed at 50, then switch to level up shield-weapon., will be back to confirm if it get unlock
ok, i remember, thanks for bring up weapon.
last usable Ultimate skill was Bezerker's Rage, hit rank 4, then got "500" since.
it was first time i ever seen "500" on ultimate, hitting the R key doesnt work, then i think i might made a change in options, going to double check, if not, then it could be glitched and semi handicapped without ultimate skill. i play ESO since last year Nov 2016's free promo trail before i got hooked.
i already maxed dual-wield skill, been on 2-handed for few months. playing DK.
sorry, nevermind, i finally fixed, now i knew why.
i had "numbers" on Ultimate in combat setting option, and then found Ultimate wasnt bind, so i select new bind, and it is now active.
thank you for making me to look and finding where it got mess up. problem solved, hope this help anyone in future issue with "500", so to be sure to check combat settings, it is quiet big menu.
i wonder why devs put that numbers on/off, must had happen changed from previous patch update. i see way too many useless features under the settings. some werent needed and should be eliminate some for latency reasons, too cluttered and messy make some specific zones very laggy.