Happy to be corrected, but, having the buy box when you are the only seller (which you would be if it is your own brand) I don’t believe should affect your advertising. I would look at your bid amount - it may be too low as I would imagine cards are quite competitive.
I don’t wish to sound rude, but just because you are a well established, and clearly profitable company already doesn’t mean things can be sped up just for you (really, i don’t want to sound rude)
Lastly, on the advertising console, you can EMail or request a call back from a representative who deals with advertising, usually they respond quite quickly, well they have for me at least
Good luck