Reboot and let it update by itself, when Avast is ready. If there is no definitions update ATTEMPT after some time (it may take several minutes, so be patient), check Avast maintenance -> update and post the resulting error shown.
It's been over two days with several re-boots, waits, and manual attempts. Not working yet
My intention was that you should reboot after the repair / reinstallation / manual update / complete VPS update.
That is, attempt to update, wait for a couple of minutes, review the info at avast main GUI -> maintenance -> update (it will tell you when the last update was attempted and what was the result), and the reboot.
Only after the reboot, you might get "real" info in the main GUI of Avast.
Please report back after following the suggestions given in several posts in this topic. If it doesn't work, there might be additional steps to try.
After you reboot, wait at least 10 minutes to review the update info, and don't force the updates (let it update when Avast can, in "automatic" mode).