The instructions above for your remote were to hit the Home Button (the one that looks like a house) at least 5 times. (You can press it 10 times, doesnt matter). Then you press the purple Up Arrow, Down Arrow, Up Arrow, Down Arrow, Up Arrow. This provides a little more detailed screen of your connection and gives us a better idea of what Roku is considering "good" or "excellent".
If you have the 3920 then you are going to have the Premiere. It is only going to operate on the 2.4Gz band of your network. It is not designed to see or use the 5gz band of your network.
The problem appears that Xfinity has merged your network into a Single SSID (single network name). It still has one 2.4gz band and at least one 5gz band but is only showing you the one name. [I think Xfinity may have told you that only the 2.4 gz led light will show connection, but that you still have 5gz connection ability]. I guess we will have to take their word for it. (You can correct me if I am wrong with what they told you.)
The problem is that with these merged SSID networks, every device that uses 5gz will drop down to the 2.4gz network when they have trouble maintaining a stable connection on the 5gz. (Basically, these devices roam for the best signal, be it on 2.4 or 5). As such, if your 5gz band is not configured properly, or you have a lot of interference on the 5gz band, more of these devices jump off and start to crowd the 2.4gz band and your 2.4gz-only devices (like the Premiere) may begin to have performance issues and just get pushed out of the way. Also holds true when your 2.4gz band is not configured properly,
Try to do the above test described before so we can actually see what your connection looks like. Also provide the model number of your router and your internet speed. (https://speedtest.xfinity.com/) You may end up having to change some router settings to get the Premiere working as it should.
In the meantime, you can see if lowering your bit-rate will at least let you watch a movie while you are troubleshooting this problem. Again, using your remote from the Home Screen...
Press Home Button (5 times), Press Rewind (3 times) Press Fast Forward (2 times).....Select Manual Selection... Then choose a bitrate. Try 3.5Mbps and see how it works. Press Home Button to exit this screen. You may have to try some different settings. You may run into some buffering, but at least should help keep you connected through a movie.
Post back with your results and will see if we can get you going a little better.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102
