After restarting the device does not connect back to the old hot-spot. The device should have to be setup again. Does the restart action mean a factory reset?
It do connect even after u r going to restart it.Once again do check the network issue if arise and do try to setup it again.
The device should get connected automatically to the wifi source to which it was connected. Please make sure that the wifi to which the device in the range of the wifi and that you have not changed the password of the same.