PayPal TEST Transactions Not Going Through
If you have enable PayPal as a payment method on your checkout form and is running test transactions with the test card 4242 4242 4242 4242 that produces an error as below:
Please use another test card and you can refer to this article from PayPal:
Try using a different test card number to test the integration and it should work.
If the integration is still not working, you are welcome to submit a support ticket.