Paypal Payment Error and Questions

Paypal Payment Error Gateway credentials are not valid. Please provide valid credentials.

How can I troubleshoot this error message? When I enter the Paypal details in the intergration it successfully authenticates.

Also another question I like to process cards via Stripe and Allow users the option of Paypal also is that the default setup if you have strip and Paypal Intergrade? I noticed the payment wall now ask express checkout and Credit Card. So if the user enters card instead of express checkout will the system use stripe?