I am using ubO too, I just purged the cache and updated the filters, still experiencing the same issue. Maybe YT is still testing this and haven't rolled out the blocking on everyone just yet?
Basically disable all current ad blockers, including YouTube enhancer ad blocker, reset filters to default, make sure there's no cosmetic filters either. And it should work L.
I just used the picker, removed the elements, saved it, and haven't looked back.
I also did this with the stack overflow nag.
Gonna try the ublock reset as outlined above, failing that I'll test uMatrix to turn off / lobotomise specific scripts.