I have a work around. For my system at least, the 6s will provision but will not get email, epo showed it as not compliant, no encryption. I know the device is encrypted, still verified in Settings. So I create policy, specifically for the 6s, until a device catalog is updated, to not require encryption.
If you're not able to get the device to provision, you may need to delete it from the database - I've seen this a few times when restoring an iTunes backup.