Activate external sync not working?

a) I saw no need for that, since the Problem seemed to be obvious to me from what you wrote (although I might of course be wrong on that)
b) You´re a bloody idiot, for missing that MIDI timecode is not MIDI clock, and as outlined in the manual, (which according to your post you´ve read), Cubase does not support being slaved to MIDI Clock.
You mean like that? :confused: I usually don´t do it that way, but could do an exception for you.

There you are…