WeatherCat Version 3.3.3 is now available. More details in the WeatherCat Releases forum.
I have just updated my Mac Mini m2 to macOS Sequoia and WC is running fine (apart from the SFTP problem mentioned elsewhere)
Sorted - it was an Xcode problemClick on the Xcode app - accept and enter password - then let it update it's stuff and then restart WC - emails working fine again.