Sync with custom CalDAV server fails with No Server Found with this Hostname error

If after the v2.0 update your custom sync server is no longer recognized, sadly this is partially expected as we’ve re-written support for 3rd party servers from scratch - which isn’t quite backward compatible. Having said that, simply go into 2Do > Preferences > Sync and setup the server again. If you had everything in sync with the server, select "Replace Local Data" when prompted how you’d like to proceed.