Unknown error encountered. Please try again!

[currong]

I am getting this error message "Unknown error encountered. Please try again!" at the checkout page.  A guest customer will see this error message when making payment through the PayPal or Credit Debit Card payment.  Displayed in red which would suggest to the customer that the transaction was unsuccessful.  However, a test purchase by myself, gets the same message but the transaction goes through.  I believe that this error message is costing me sales.  Can you suggest a fix.

[Basara]

Hello.
What is your AbanteCart version?
What is your theme?
What is your checkout (regular or fast checkout)?
What is your PayPal extension?

[currong]

What is your AbanteCart version?
I am using v1.3.3

What is your theme?
Theme is default that came with the installation

What is your checkout (regular or fast checkout)?
Regular checkout, fast checkout is turned off

What is your PayPal extension?
Paypal Commerce update 20/11/2022

[Basara]

Hello.
Please enable Fast checkout