I hope DB can help you with your purchase.
Sam writes, "7-day continuous 2nd cl passes. GRP is offering 424 EUR for the same thing, Twin is offered at 318 EUR."
Yes - I mentioned the continuous/consecutive twin pass promo price of €318 on your previous thread as well... But that would also require a credit card purchase through DB, and you'd still need to buy a day of travel to or from MUC airport.
I haven't looked at Raileurope. But if your chat with DB isn't fruitful, and if you have to pay $540 (€454) at Raileurope, as Sam has indicated, then why not just buy the German Rail Pass from DB once you arrive in Germany?? It's cheaper and you can buy it right at the airport, you know...
The normal DB price for a 7-day CONSECUTIVE twin pass is only €398 (then you need to buy one airport trip at €22 as well.)
The 7-day FLEXI twin pass is €416 - that covers more than all your travel days, I think, so it's even better.
The best deal is likely the 5-day FLEXI twin pass at €335, regular price (on top of which you may need 1 airport trip at €22, not sure how many days you will actually use trains.)
And of course you'll get personalized help from the DB agent at the station and you'll be able to ask whatever questions you may have right there. And by avoiding online purchase, you have no worries about online procedures or things getting lost in the Christmas season mail rush, etc.
DB page source for mormal GRP prices: https://www.bahn.com/en/view/offers/passes/german-rail-pass-conditions.shtml?dbkanal_007=L04_S02_D002_KIN0060_GERMAN-RAIL-KONDITIONEN_LZ01
If DB can't help you with your credit card problem and the 7-day promo pass you want, I would just confirm with your DB contact that on your arrival date, the GRP prices at the ticket counter in Germany will be the same as the GRP prices stated above - and buy them there.