ZTE MF75 - Manual (Page 18)

Resetting to Factory Defaults
1. Remove the back cover of the modem and then plug it in to a
computer or power adapter. Make sure it is turned on.
2. Using a pin or paperclip, press and hold the reset button for 5
seconds. Check the MobiiConnect 4G Overview at the beginning of
this guide if you’re not sure where this button is.
3. The status lights will blink and then your MobiiConnect 4G will
restart.
4. All custom user configurations and passwords will be wiped and
the settings (e.g. SSID, passwords) will return to factory defaults.