I take it you mean that the Ethernet stopped working, as the Unitiserve has no WiFi.
There may be an IP address issue if the repaired unit has had its software reloaded, or a factory reset. The first thing I would try is a router restart. If that doesn’t work, a full network restart might do it. That means turning off your router, Unitiserve, computer and any other devices. Then turn the router back on, and let it fully start up. Then start the other devices one at a time.
If that doesn’t work, you may need to dig a little deeper.