There not enough information in your description to provide a specific analysis.   Please open a PMR.  Depending on whether or not the issue is an authentication issue or a sync issue,  the support team will want to collect logs to understand in more detail why the device cannot "reconnect".   Typically we start with sync logs for one of the device: http://www-01.ibm.com/support/knowledgecenter/SSYRPW_9.0.1/UserSynchronizationProblems.dita .   Since the users are able to authenticate via a browser on the device,  this would push us in the direction of asking for sync logs.

Also please note,   running a reset is typically not recommended unless directed by support.  In many cases,  the reset just causes the whole sync process to start over again, and eventually, the device gets back to the same point of failure.