What was the payout for that game if you were in a Coalition...?
Remember... If you start a Coalition... and have only you as a member... it's still a Coalition getting Coalition payout.... not a Solo payout.
If you want a better payout... Start a Coalition... then once you have more points than needed for Solo Victory.... BUT BEFORE you reach 65% of map VP and score the Coalition victory.... Drop the Coalition... and you will get Solo Vicotry with the Solo payout+VP you earned.
You will NOT trigger a Solo Victory if you reach the points needed (45%) but are in a Coalition.
Also... put in a Support Request ticket.. and ask.. though I'm not sure what else it could be.