I was on 6.12.8, and I can't update to 6.12.10. I was able to update to 6.12.9 however.

 

When I try to update to .10, the pop-up screen shows:

plugin: installing: unRAIDServer.plg

Executing hook script: pre_plugin_checks

plugin: downloading: unRAIDServer.plg ... done

 

plugin: not installing older version

Executing hook script: post_plugin_checks

 

I have tried changing my DNS to 1.1.1.1/8.8.8.8. I saw someone had a similar issue with downloading plugins.

You can always do a manual update:

 

https://docs.unraid.net/unraid-os/manual/upgrade-instructions/#manual-upgrade-or-downgrade

That worked, thank you. Never had to do that before. I have two unRAID servers and the other one updated just fine.

Exactly the same situation. I was on 6.12.6 and the update to 6.12.10 fails the same way with 

plugin: not installing older version

 

I thought it must need to got to 6.12.9 first, which installed fine. Still no joy with 6.12.10.

I'll do the manual update, thanks @JorgeB

Same issue for me "plugin: not installing older version" on a second testing server. Its offline a lot of the time (waiting for v6.13/7) and doesn't have auto updates for docker or plugins setup like my production server.

I went to the plugins page and found the "Unraid Connect"  plugin needed an update. Once complete the update worked as normal.
You may need to "Check for updates" from the plugin page to get any updates to show up.

 

Updating plugins (specifically Unraid Connect) is the correct solution here. If you do a manual install, be sure to update plugins after booting into the new OS.

Quote

I went to the plugins page and found the "Unraid Connect"  plugin needed an update. Once complete the update worked as normal.
You may need to "Check for updates" from the plugin page to get any updates to show up.

 

This fixed it for me, thank you.