Hello Mitchell,
You can go over the Roku troubleshooting steps here, I would also reboot your phone, make sure it is up to date and is connected to the same wifi network as the Roku if the Roku is on 2.4GHZ then make sure the phone is on 2.4GHZ network or 5GHZ & 5Ghz if that applies.
I would also try clearing the cache on Roku, you can click here to see how.