Since ver. 5.2.0
PushServiceConnectionClosedError
Thrown when the connection to the Voximplant cloud is closed before a pending PushService.registerPushToken or PushService.unregisterPushToken request can complete.
This indicates that the registration or unregistration process has been interrupted by a loss of network connectivity or a manual client termination.
See: PushService.registerPushToken, PushService.unregisterPushToken