Could you explain what you mean by: “the MAC address of this PC has changed”? You can contact email@example.com for license issues/updates.
In general, though, if you’re running groov Server for Windows w/out a license (e.g. the “free trial” version), the only thing that stops after 2 hours is the communications to your various devices, e.g. Modbus, SNAP PAC. You can simply stop/re-start the server to get another 2 hours.