Please try the following troubleshooting tips:
1. Power off you Roku, modem, and router for at least 60 seconds
2. Make sure you're running the most up-to-date version of the UMC channel
Visit Home/Settings/System/System Update/Check now to update your system
3. Connect your device directly to the router via Ethernet cable.
4. Disconnect other devices from your network.
If the problem persists, try removing and then reinstalling the UMC channel:
1. Press the (*) button on the Roku remote
2. Select "Remove channel"
3. Visit the Channel Store and search for "UMC"
4. Select "Add channel"