I can't seem to download V22. That is, when I have the OS-4 booted up and display the status page it shows V21 and no updates available. Both Upgrade to Beta Versions and Automatic Upgrade to Latest Version is checked. Clicking check for upgrades returns with no upgrades available. I have been able to update to Beta versions in the past.
The latest stable firmware version is v24. You can find more information about the latest version check process in the device log on the Status page. Make sure Advanced mode is enabled at the bottom right of the web interface to see the device log.
In a similar vein I am stuck at Version 22. Won't update to latest Version 24. Log shows JSON error on trying to check.
20:09:57 fwu-chk: start
20:09:58 fwu-chk: json process error
20:09:58 fwu-chk: err, retrying
I unchecked Upgrade to Beta Versions under Settings. This allowed me to download V24.
Unselected Beta updates also worked for me. Now back up to V24.
Thank you for reporting the issue, it'll be fixed in 24 hours.