PayPal Plus ends with a server error 500

-- url of the page with the problem -- : shop.the-flying-condors.de
-- HikaShop version -- : 6.5.0
-- Joomla version -- : 5.4.6
-- PHP version -- : 8.3.29
-- Browser(s) name and version -- : Google Chrome
-- Error-message(debug-mod must be tuned on) -- : Server Error 500

Today I noticed by chance that the payment method PayPal Plus does not work anymore.

If I use the button buy now I get an internal server error 500.

Is there anything I can do to fix this issue?

Greetings - Harald