Did you install ActiveVOS at the same time as MDM, or did you do the MDM and ActiveVOS separately? From what I've read before on the forums, best practice is to do it at the same time so items like the identity service and the OOTB workflows are loaded into the ActiveVOS configuration.
Actually has you reinstall MDM (in a limited manner) if you want to install ActiveVOS after the MDM installation.
Hope this helps!
I have installed ActiveVOS along with MDM installation.