I have v0.0.8 of the Extension manager with v2.8 of the Heyzap extension. In the Heyzap-master folder, I have version 4.0.6-r2 of the Vungle framework. Which I don't think is the latest version, but I think I had compile error when I copied the latest version into there. It's the same version as is in my Vungle extension folder (in engine-extensions) which appears to work.
You don't must have the 4.0.6-r2 vungle framework inside the heyzap extension, it must be in the Vungle extension framework folder and the embeddedframework has to be in th template->PROJ-Classes folder.
You cannot update the framework by your self, because the extension manager has to be updated also.
As colburt already said, test ads are active for Vungle in Heyzap if you enable test ads in the Vungle Dashboard.
I advise to re-install the extensions (vungle and manager) and follow this tutorial https://github.com/byrobingames/heyzap/wiki/4.-Error-on-Compiling
to add the vungle framework inside the vungle extension and not in the heyzap extension.