Cannot re-activate F-Secure on Mac OS

Thanks for thinking along!

Issue: we have F-Secure on an iMac. Normally works fine on all our other Apple notebooks. And this iMac. Yes, we do have enough licenses for all...

After downloading an update, the software is being properly installed. However.... the software does not activate itself after logging in with our F-Secure account (yes we used the correct credentials, we can also enter the my-page via the site witghout issues).

We get a mesage saying "Activation failed. Please try again later" (or slightly different words, but same message).

When checking via the my-page via the browser, we see a new machine added every time with an exclamation mark (like something did not go well). Obviously we removed all these erroneous licenses to prevent exceeding the number limit.

We tried removing all programs related to F-Secure, forced-closed the F-secure app running in the background. Instaled everything again etc, etc, etc... 

Does someone have an idea where to focus my problem-solving skills and make it work again?

Thanks!