Effectively it couldn't have been stuck on 120921-0 for two days as that is only yesterday. Depending on the release time of that update (seen in the avastUI,Maintenance, Update) possibly still within a day. Remember there is also time zone differences, with European Central Time being in advance of the USA time zones, this can have an effect of being overdue.
If it reports up to date yet the VPS version is more than a full day old, then that is unusual. This happens on occasion, where the displayed VPS and actual VPS, reported as up to date when a manual check is done are different (out of sync). In which case an avast Repair will usually resolve the out of sync condition, a reboot may be required after a repair.
