I recently ran into this error when trying to put someone on a new blackberry (Q10/Z10)
Too many devices are connected to this account
I read a lot of information online but I didn’t find any forums with a fix. Another tech in our group finally found the solution.
You need to get the user to login to OWA and go into Options, Phone.
In here you will find all devices they have listed in their account. The default limit is 10 devices in Exchange. Going into OWA this way will let you clean that up. This won’t apply to most users unless they swap devices often for testing.