as the dev tools tell me, the request to https://ddv-media.de/hiddenapi/lp/v1/courses/enroll-course?_locale=user fails and tells me there is no such path.
We did not change anything in that regard. Plus, as stated, the URL are both containing /hiddenapi/ – the problem is, that the request URL is followed by /lp/ while there is no such path, but there is /learnpress/.
Learnpress get link API domain by site, and define /lp/ , /learnpress/ is 2 type API. LP make API from v4.0 and the first time we see this problem. We think something wrong config on your site. You find link support on the https://wordpress.org/plugins/learnpress/ and create a ticket, we’ll check more.
We use your plugin out of the box. In the network tab inside the dev tools we can see it sending a request to /hiddenapi/lp/… which returns, that it does not exist. Checking for a path myself the api endpoint is at /hiddenapi/learnpress/…