Thanks for the replies! Good questions/observations. I will check later today, but I'm pretty sure I'm at level 8 or 9 with my characters. Don't quote me, as maybe (slight chance) I am 12? I know my spells for Shadowheart and Gayle are still at VI. I don't know if they ever go higher than that?
I definitely haven't installed any mods, or added any dummy levels, or anything like that. Just the plain, basic, vanilla (albeit awesome) game, and I let Steam install it however it installs it.
A month ago when I emailed Larian about it, I took screenshots. My XPs at that time were at about 8600 for two in my party and about 9150 for the other two. I will see what it says now, later today/tonight, and report back.
In my email over a month ago, the Larian agent replying seemed to think it was a known issue (an exceept):
"This is a known issue that the team is currently looking into.
We're constantly rolling out hotfixes and patches over the coming weeks and months, but unfortunately this issue isn't currently solved.
"While we work on it, be sure to follow us on social media, and check out either the Larian Forums, where we're constantly providing hotfix and patch notes: Baldur's Gate III - Latest News - Larian Studios forums
"In the meantime, know that we're working on this problem and we hope to have a fix on the way to you soon."
I figured I would write here since they suggested looking at the forums, and I'm still having the issue over a month later. Seemed like a pretty important bug, definitely makes me miss the level up process, but I'm sure other players have found worse bugs than this. So I don't know where this one would rank in priority.
Then again, maybe I just haven't gotten enough XP in a month to level up yet... but I wouldn't know since my XP bars are blank. So it is invisible XP. (I do still get the "+250 XP" pop-up text over character heads when I complete quests, though.)
Regardless, I will double-check to see if I am already at Level 12.