Just posted this to another thread... This is most likely your solution:
This problem can be caused by client certificate authentication in iis. I don't know the exact location off the top of my head But it must be set to "ignore client certificates".
If you provision and the enterprise activation certificate disappears, check for this setting.
I have the same problem on 1 of my iPad 2.
I have installed EMM to 20 iPads without problem, but this problem appear to only 1 particular iPad. I tried using different username but it just can't install EA. I also tried to restore my iPad to default factory setting many times but it still the same.
Appreciate if you can advise me on this.
Thank you very much.
Sounds like a different problem since it's only happening to 1 device. Have you tried uninstalling the profile and deleting the device from the EMM helpdesk then reprovisioning? Also ensure that the network that the device is on allows it to communicate with the Apple push servers.
I have tried uninstall the profile and also restore the iPad to default setting with 3 different computers, also tried using both WiFi and 3G connection.
The EA profile still doesn't appear.
I ended up having another issue that resulted in rebuilding my server before I was able to get resolution on this, and with the new load the problem disappeared. I concur with Mat's responses - have you verified that the problematic iPad is running the same iOS version as the others?
On a side note I have noticed in earlier versions of EMM that the EA profile would ocasionally take a while (up to a few hours) to finally show up on an individual iOS device but haven't noticed that since installing 10.x.
All the iPad is running on the later iOS 5.1.1 (9B206) and was restored to factory default using iTunes 10.6.1.7 (tried on 3 different PC's - XP Pro/Vista Pro/7 Pro).
Yesterday night, I tried to restore at Home with my Vista laptop (previously without any iTunes installed), downlaod fresh iTunes and EMM from App Store; and it still the same.
This is really strange, I have no issue with the other 19 iPads but only this particular unit is having this problem.
Managed to solved the problem. Just launch the EMM App on iPad, signout from the app, re-enter the password and login in again. And it works!
Thanks Mat and Shawn!
Glad to hear it's sync'd ...wish I knew why but sometimes it's like the gremlins go away for a bit and things you've tried before start working.