I have the exact same issue. I cannot log out or shutdown my system by either using GUI log out or through the terminal using "gnome-session-quit" (for log out)
Error message: Failed to call logout: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.SessionManager was not provided by any .service files
Linux XXXXXXXX 4.15.0-72-generic #81-Ubuntu SMP Tue Nov 26 12:20:02 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
I have the exact same issue. I cannot log out or shutdown my system by either using GUI log out or through the terminal using "gnome- session- quit" (for log out) org.freedesktop .DBus.Error. ServiceUnknown: The name org.gnome. SessionManager was not provided by any .service files
Error message: Failed to call logout: GDBus.Error:
Linux XXXXXXXX 4.15.0-72-generic #81-Ubuntu SMP Tue Nov 26 12:20:02 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux