[dunhill]

Hi, thanks for the report! This is actually expected behaviour, not a bug. You’re running a Beta build of calibre (9.16.100), and as the message says, the plugin deliberately doesn’t install anything over a Beta. It only lets you know when a new stable version is out, which it did correctly with 9.17.0.
Also, Betas can be set up in many different ways depending on each user: installed over the stable version, in a separate folder, renamed, alongside a Portable copy, and so on. There’s no reliable way for the plugin to know which setup a user chose, or which copy they want updated, so overwriting anything there could easily break someone’s installation. That’s why the plugin only handles the standard stable installation automatically and just notifies on Betas and Portable versions. Users who run Betas are usually experienced enough to update them by hand, while the plugin is meant to make life easier for the typical calibre user with a single stable installation.
If you are using a portable version, the notification will look like this.
Betas are meant for testing and may contain bugs, so keeping them separate from the plugin’s automatic updates avoids confusion and protects your stable installation.