I also couln't pay with debit card, so I clicked on pay with paypal. I normally filled my personal info and pressed proceed with the payment and it takes you to another page where you can click pay with credit or debit card under it. Then it takes you to another page where you just fill your email and then you just fill in the info of your card and you get the game. (at least, that worked for me :D)
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@princessiiria as a reply im also from the netherlands sadly paypal doesnt support dutch credit cards like ing and abn were jut gonna have to wait till there comes a possible solution like cutie releasing it on steam but thats up to her (she cant do anyhting about the credit cards neither can itch io)