If you were flying AC there would not be any issue with the extra baggage allowance as AC has real-time availability to your AE account. Deleting your number and re-entering would work fine. In my experience it sometimes takes time for status changes to be reflected in UA's systems.

You should probably cancel your check-in, repost your number, and then check-in again.

When "fighting" tomorrow, keep in mind that technically the new status year doesn't start until March 1 and that you won't have your only official documentation of your status (i.e. your AC*E card).