Due to an bug that affected the updater, after the update was installed Sonarr was unable to start because Sonarr.exe was incorrectly in a subfolder. We’ve pulled that update, but it was live for ~3 hours so several users would have updated to that version automatically.
We’ve fixed the underlying issue and we’re working on preventing a similar issue from happening in the future. Thanks to everyone that reported the issue quickly.
You’ll need to install Sonarr on top of the existing installation, no need to remove first.
For docker, update the container again.
For other platforms follow the installation steps for your platform on https://sonarr.tv/#downloads-v3