This is an upgrade from 3.0.4 to 3.0.5
I had this happen today with one of my M2500C adapters (2 others had upgraded just fine).
I gave it a few minutes and nothing changed (also tried incognito window, same issue) and finally power cycled the unit and things appeared to be fine after that.
Looks like the broswer has some caches. Could you try another broswer and check the management web?