First, reveiw everything you did, or attempted to do, with your bank account over the last month. It's likely your actions triggered suspicious activity alert and determined that using your bank account was high risk, so it is permanently disabled.
Next decide whether you want to phone PayPal customer service and talk to an agent to see if it can be fixed, or just open a new bank account. Make sure you don't do anything that would raise suspicion with a new account.
