Hi @rednewsch,
While entering your iCloud username and password, you have the option to check "Keep me logged in", in my case it's in dutch "Houd me ingelogd". That are all the checkboxes you need to set.
After that you will get the popup, and you have to open Enpass if it doesn't happen automatically.
You will then see that synchronization is started
and after a few seconds it is ready.
If you then go back to your browser, the spinning circle is still there.
You can just close the browser at this point, because the setup is already done.
Hopefully the screenshots will help you foreward.