I went thru the same thing last weekend:

Friday -- flew STL-DTW-DCA, which would yield enough miles for Plat

Saturday morning -- nothin'

Sunday morning -- miles posted, status change effective Monday, checked in as a GE anyway (wife was SE in same record) for Monday flight

Sunday evening -- kept trying to re-enter WP #, kept showing me as GE, finally about 11:30 p.m. EDT it worked and the itinerary showed me as PE (but I had already entered the waitlist as GE)

Monday morning -- printed dup. BP's at kiosk (showed me as PE), then stopped at WC to check on my priority & position in the waitlist, was advised that I was #1 but as a GE, so I showed her my BP and told her I was PE as of that date and would she please update the waitlist info, which she did. My first upgrade as a PE was a battlefield upgrade on DCA-MSP.

So if it's not too late to salvage/improve your upgrade chances, I would suggest:

(1) If you have computer access, keep trying to change your WP number until your itinerary shows your new status

(2) Use a kiosk to print duplicate BP's (or the hotel printer/fax if available), so you have a hard copy that show's you're a Plat

(3) Arrive as early as possible and show the hard copy to a WC CSR or TA/GA and make sure you're in the waitlist correctly. WorldClubs seem to be the best for that since they're less harried than the people at the ticket counters and gates and they're much more understanding of "high maintenance" customers.

The hard copy really shouldn't be needed, but it never hurts to have some physical evidence.