Why does PayPal do this?

Hey,

I have a question because I'm not really getting the hang of PayPal at the moment. When I bought two season tickets for the MEX convention through PayPal, everything was fine, everything was normal. Now, when I wanted to order something from Killstar, they wanted my bank account again and somehow won't accept it.

The first time I tried to order something (this time a pre-order from Uwowo, but it was apparently already sold out), I also had problems. I called PayPal support the next day, and the employee was very friendly. He explained to me that my account is still new and PayPal thinks there's no money in it. But I don't know if that's still the case, or if they sometimes think that.

Does anyone know why or can suggest a solution?

Would be grateful for any help!