No Rewarded Video Button If Vungle Not Integrated Ay Android!

Hi all,

I have an issue with heyzap mediation. I can integrate it without a problem both at ios and android but somehow at android if I don't integrate vungle with other ad platforms (I use admob, vungle, unity and chartboost) The rewarded video button do not show. I don't believe it has got to do with fillrate because even vungle works in the next videos unity videos are also available after a short time. But in the other way if I don't integrate vungle and integrate all other platforms the button never shows up even I wait like around 30 seconds etc. Does anyone face this kind of problem? I know this sounds weird but it is the way it is. I even tried to integrate vungle and then turn off from Heyzap and in that way the rewarded video button goes away again.

I would appreciate your help

Kind Regards

Volkan