Unknows error when finishing PayPal payment

-- HikaShop version -- : 6.5.0
-- Joomla version -- : 6.1.1
-- PHP version -- : 8.3.31
-- Browser(s) name and version -- : Firefox 151.0.2
-- Error-message(debug-mod must be tuned on) -- : Error in front-end after the login-modal for PayPal:

Unknown error when processing order

Even with debug mode on and error-reporting on maxumum there is no more information, but the payment is not completed.

Since two weeks I get an error in front-end after the login-modal for PayPal.

Unknown error when processing order

I am using the PayPal checkout plugin


Even with debug mode on and error-reporting on maxumum there is no more information, but the payment is not completed.
The website worked for many years without problems.
Updating tot Hikashop 6.5.0. did not make a difference.