If you are currently running version 1.2.7 you’ll need to install the “Updatefix 1.2.7” plugin from the plugin repository before you can update your OctoPrint installation.

Version 1.2.7 sadly contains a bug that breaks updating OctoPrint. When attempting to update, you’ll simply get presented with an “update successful” message, but nothing was actually updated. Version 1.2.8 contains a fix, but naturally we have a hen-egg-problem here. To allow you updating to 1.2.8, a plugin was made available that basically backports the needed fix to 1.2.7 by monkey patching your existing installation during runtime: “Updatefix 1.2.7”. It can be found in the plugin repository and can be installed directly through your plugin manager - just refresh the plugin list from the repository (via the little wrench icon in the plugin manager install dialog) if it doesn’t show up immediately when you search for “update”.

The section “A bug in 1.2.7 prevents directly updating to 1.2.8, here’s what to do” in the release notes explains everything and also offers you a work around if you can’t or don’t want to install the plugin. The FAQ has been updated as well.