All right, I got SVP4 working again.
I uninstalled everything related to SVP4, reinstalled it again - no change.
Uninstalled and reinstalled Kodi DSPlayer - no change.
Finally uninstalled SVP4 completely, and unregistered the license key for my HTPC via the License Manager site.
Then reinstalled SVP4, rebooted and input the key again and now it works.
Basically I think there is some flaw in the license key management of SVP4, it might need to check this differently and needs to ask immediately for the key, not only after boot (SVP did not ask for key right after installing, at which point it still didn't work). This is consistent with the fact that two days ago my license key was moved to another email address, SVP did not recognize this move and thus got messed up, is my theory.