When buying something from HB with Paypal, it's telling me I have to verify my CC but I already did.

Maybe even HB got you flagged as a scammer

Some sites require that when using Paypal, you must have a backup credit card attached to your Paypal account. Having enough money in your Paypal account or a bank account attached is not enough. It may also depend on what country you are in, as I don't usually see this problem mentioned by North American Paypal users, but hear about it a lot from folks in Europe and elsewhere.

Especially happens to new users depending on the website of the shop and how frequently you purchases sth. ... Not really sure how it exactly works but I got the same issue sometimes.

Those are new protections - some banks use them, some don't. That is all. It is quite random.

Fixed now, thanks everyone!

(Also paypal support sucks, they said they will reply back in 24 hours and it's over two days.)