No connect width Paypal

-- HikaShop version -- : 6.1.1
-- Joomla version -- : 6.0.0
-- PHP version -- : 8.4

Hello,

I upgraded from version 5.0.0 to 6.1.1. Now I can no longer connect to PayPal. When I click “Connect,” I get the PayPal message “This page does not exist.” When I enter the client ID and client secret, including the merchant ID, the connection to PayPal is rejected at checkout.
What is the problem?

best regards
langi