It's too late for your upcoming flight but for potential upcoming CO metal flights have you linked your MileagePlus to your OnePass account to receive Platinum status on CO?

While the upgrade priority chart is somewhat confusing regarding order of status levels clearing on CO metal, my school of thought is always use the operating metal's FF program. For CO I use OnePass and for UA use MileagePlus. Both accounts will be combined at the end of the year or when you reach another status level.

Link Accounts: https://secure.unitedmileageplus.com/MP1101OP.jsp