If a device is not able to send messages to Device Manager due to, for example, loss of connectivity or the Device Manager Server is down, the device uses an exponential back-off strategy to connect i.e. after 5 seconds the device will retry, then after 20 seconds, etc. until the timeouts are reached. The timeouts are configurable on the device as well as the max connection attempts. Once the timeouts have been reached, the device will only try again on the next configured upload, i.e. heartbeat, in trip upload, etc.

For Edge devices, if the device has sent messages successfully to Device Manager but the Location Engine is not able to forward messages to the 3rd Party platform due to, for example, the server is down, server returns an error, or responds incorrectly, the Location Engine will keep retrying until it’s able to deliver the messages. After 7 days these messages expire. 

[ExponentialBackoffRetry(-1, "00:00:04", "00:15:00")]

i.e. will retry indefinitely starting with a 4 second interval working up to a maximum interval of 15 minutes.