Payment declined even though cards work properly

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I have been my UnionPay card normally for about a month until it suddenly it got declined today when I tried to pay another invoice. The card has more than enough balance to pay and works fine in transactions other than PayPal.

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And for a little bit of context, this is actually the 2nd card that got declined.

Originally I had my MasterCard linked and I have been using that card to pay since late last year until it got declined at about a month ago. Asked the bank and they said I've reach some sort of limit and advised me to link another card. So I linked my UP card and it worked for a month or so until now. The money sent from my UP card is not even 1/10 of that from the MC card, so there is no way I hit the limit again, right?