I've been trying to Screencast on my ruko express and it won't connect to my windows computer or my galaxy s9. I've tried the steps of changing the settings and those haven't worked. It will shows the screen asking if I allow them to connect, attempt to connect for a few seconds and then just stop and go back to the home screen. Anybody have any ideas on what to do
1) Make sure you have the latest RokuOS version/build - Settings/System/System Update/Check Now
2) Reboot the Roku/Phone/PC
3) Try again, make sure you select "Always Allow" in the Roku dialog box
Beyond that, there is a bug in 9.3.0 that prevents Miracast connections with some more recent Samsung Android 10 devices and OneUI 2.x and SmartView when the Roku is connected to 2.4Ghz-based networks (this may apply in your case, since your Express is 2.4Ghz only and you have a Samsung phone).
If the above steps dont work, and if your Samsung has Android 10 and One UI 2.x, please report the bug to both Roku and Samsung: