Sandbox account not working

Hi,

I am trying to connect your plugin to our sandbox account but it does not seem to work either way.
If I use the connect button I can login to Paypal but then receive a few error messages, first that I am offline, then the client_id is required and third time is the charm it seems to work but it uses credentials for the API that are not from our sandbox development API.
Subsequently the API calls also fail on the checkout page.
When I enter the API data manually (also created the webhook) it shows connected but the API calls also do not work.
I have debug log enabled but there is nothing in there except those error messages:

2022-10-28T05:08:52+00:00 ERROR API error: Array
(
    [url] => https://api-m.sandbox.paypal.com/v2/checkout/orders
    [method] => GET
    [request] => 
    [error] => 
)

Any idea what is going on?
If I try the official Paypal Plugin from Woocommerce it works fine, also our old Paypal plugin works without issues.

Best and thank you
Sven