Can some one point me to a dicussion on how to upgrade in situations like this like OP described. A mix of UA/CO/UA Ex/CO Ex

I am doing a IAH-RDU trip this week. (UA 4684)
Bought tikt on UA, .bomb says opetated bu UA express/Skywest
But UA agent says its operated by CO Express

After the status match, my CO profile says *Gold due my 1P status.
But recently I flew to IAH-SAN and though I bought my tikt > 2 months ago and it was quite expensive fare, somehow I missed UG. Maybe I was down on the list but I want to make sure I am not missing anything on my part that I need to be doing.
thanks