I suspect that Orange have stopped accepting your Tuxedo MasterCard because as of July this year they launched their own "Orange contactless cash card", basically they have launched their own prepaid card. This makes every other prepaid card the "competition" in the eyes of Orange, they will make more money from fees etc if they keep it in the family and refuse to accept other types of prepaid mastercard.
What I am not sure about is how they have managed to get away with this, if you display the MasterCard acceptance mark, then it means you must accept all mastercard payment products, regardless.
I found this out the hard way, purchased a prepaid mastercard for my 13 year old son, delighted to find a safe way for my son to spend his pocket money and learn to top up his phone himself. He is on Orange and I found out pretty soon that we were unable to top us using prepaid mastercard (MeCard). So I spent a long time on the phone to both parties before finding out that MasterCard are in talks with Orange to try and straighten this out. They should never have let this happen in the first place in my opinion!