This feature is only available to Proxidize Personal and Proxidize Business plans.
By navigating to your endpoints page under the hardware tab, you'll be able to find the reboot endpoint modem under the endpoints action dropdown list, this action remotely reboot the endpoint.
You'll also be able to reboot modems in bulk by ticking the checkbox next to each modem you want to reboot (this feature is also only included in Proxidize Personal and Proxidize Business plans)