iPad enrollment time out

[vyperz]

So, i have 32 ipads on the Apple Profile Manager etc. Am trying to add another - have created the user, prepared & supervised it on Apple Configurator, now I'm trying to enroll it for VPP app distribution - I send the invitation to the user device , go through the steps of logging in with Apple ID, accept the terms & conditions and then it says "Yoru sessionhas timed out. Try again" I have tried around 40 times , i have reset the network settings on the device, created an new Apple ID, cleared the Safari cookies, tried different wireless LAN's (we have a few different ones), have even erased and redone the device twice. Last time I did it , it worked after about 3 attempts ( and resetting network settings ) - i am now at my wits end ! Any ideas??