You may not have a credit card or alternate funding source attached to your PayPal account and the seller has disabled eChecks. Please see PayPal eChecks Explained for more information.
2. Update your payment details.
You may need to update your credit card or billing information in your PayPal Wallet.
3. Seller Pay Anyone Issue.
The Seller’s account may be set to block payments when the payment is initiated from the "Pay Anyone" subtab of the "Send Money" tab. The seller may be unaware this setting is enabled.
While the payment from a BrickLink Buyer to a BrickLink Seller is being initiated from bricklink.com, PayPal may treat it as if it was initiated from the ‘Pay Anyone subtab of the Send Money tab’.
Here are the steps for the Seller to resolve this issue:
Log into your PayPal Account (again, the Seller is doing this)
Select ‘My selling tools’ in the left sidebar
In the ‘Getting paid and managing my risk” section, click the ‘Update’ text link adjacent to ‘Block payments’
In the ‘Block payments from users who:’ section, uncheck the box for “Initiate payments from the Pay Anyone subtab of the Send Money tab”
Scroll to the bottom of the form and click ‘Save’
4. Seller May Not Have Set Up PayPal Correctly.
It's possible that the seller may not have set up their PayPal account correctly to receive funds. Please contact paypal directly to ensure your account is able to accept funds.https://www.paypal.com/us/cgi-bin/webscr?cmd=_contact-general
5. Additional PayPal Settings To Try
Account Spending Limits: PayPal implements certain limits on the amount of money that you can send. If you're paying as a guest in PayPal, you will not be able to contribute more than 500 (USD, EUR, GBP, or CAD). You will also only be able to use PayPal's guest checkout process up to 15 times with a total spending limit of 4,000. Once you reach PayPal's maximum, you will be prompted to upgrade to a full PayPal account.
If you're paying with your PayPal account and receive an error message after attempting to pay claiming that you exceeded your spending limit, we recommend contacting PayPal Support directly.
Account Balances: PayPal cannot process transactions if the balance of the PayPal account is too low. The balance of the PayPal account must either be positive and cover the cost of contribution, or the PayPal account must be linked to a credit card that provides sufficient funds. Please note that if you link your PayPal account to a credit card, it may take several days for PayPal to confirm your credit card. Hence we recommend buyers and sellers contact PayPal directly on specifics regarding the wait time for this verification process.
Please contact PayPal directly to resolve issues with your PayPal account.