Paypal continually subjects your account to verification to confirm your identity, location, or contact info. The main things they want from a US account is to confirm a bank account and a card that is associated with you. In addition, they usually want the card to verify the address you listed in the account, and eventually may ask for a SSN/TIN the government assigned to your name.
If you don't have a functioning bank or card account to attach to the PP account (or can't because it's a stealth or pseudonym account), you'll have to get a virtual bank account and virtual credit card (VBA and VCC) that PP will accept to confirm/verify your account. Depending on how suspicious they are, you may have to perform other verifications. Several vendors on BHW and on the web offer VBAs and VCCs, try one to fulfill your needs.