I’ve run across a few posts here regarding this but I have yet to see a solution. When attempting to add Nextcloud Calendar and Contacts, eM Client successfully finds the services, identifies that Nextcloud provides calendar, contacts, and notes, but does not assign folders automatically. When I attempt to assign the folders I receive “The folder you selected doesn’t belong to this CalDAV account or isn’t an event folder. Please select appropriate folder.”
I’ve attempted to created new local folders as well, in case for some reason eM Client doesn’t want to use it’s pre-existing Calendar, Contacts, and Notes folders.