in order to help you, we would need to know which model/product you are referring to.
Also, why do you need to reset it? Just once or is something you need periodically/automatically for any reason?
If the device is SarOS router, I can suggest you this:
Otherwise, our support site contains lot of documentation basing on the model:
If any further help is needed for this, please send us an email to email@example.com providing also the SN/IMEI of the unit.
Please also review Support options here: https://www.digi.com/support
Digi Technical Support