Accepting a vpp invitation with no app store

[Hackert]

I am sorry, but I can't find an answer for this anywhere.  I have used VPP invitations for years, once a student accepts it, I can push iBooks to their iPad.  I have also always used the self service portal for apps and removed the app store.

In the past, a student would receive the invitation in the self service portal, register in the app store (which would open just for a moment to accomplish this), and done.

This year, they get the invite, click Register, the app store opens for a split second and closes much too quickly for them to agree to anything.

Thoughts?  We are up to date on our JAMF console and use ASM and DEP.

Thanks.

[Greenholt]

VPP Managed Distribution invitation URL does not seem to work only in iPads on iOS 9.3.2. The Invitation URL which begins with "buy.itunes.apple.com" is supposed to open in iTunes app and prompt the user to accept the terms and conditions to join VPP program.