The software does not operate correctly with Mac Tahoe 26.0.
It worked for a couple of days, but then it got extremely sluggish, with spinning wheels every time you clicked something. I have given up trying to use it until this can be fixed.
I have tried deleting the plist and cache files and re-installing the software without any improvements.
The software does not operate correctly with Mac Tahoe 26.0
First suggest to update your Mac to 26.2 as there has been alot of Mac OS changes.
Then check that you have the latest version v10.4.4293 as there was updates recently. This version works fine for me on two different Mac Mini M2 Pro with Tahoe 26.2
To update, close eM Client and then d/l the latest Mac v10.4.4293 from the release history page and install that and see if that fixes it.