This happened to my Roku Express 4K+ over this past weekend. If I streamed in any app it would kick me back out to the main menu after 3 minutes. I didn't want to do a factory reset but I tried everything else that I could think of including rebooting my modem and router. Nothing worked. So finally on Monday I did a factory reset and endured all of the busywork required to get everything set up again. And the problem was solved. But for only one day! On Tuesday evening the problem reappeared.
I was so annoyed that on Wednesday I got out my old Roku 2 (4210X) which hadn't been used for 9 months or so. I set it up and waited while it went through 75 updates! Then I started streaming a newscast from MSNBC on the NBC News app. And after 3 minutes it kicked me back out to the main menu. On my old Roku 2!
It happens that during a Black Friday sale last month I bought one of Roku's competitor devices. I bought it just to experiment with and maybe keep as a backup. But now it is my only working streaming device.
I will keep checking on my Rokus (both of them!) once in a while. I'd like to be able to come back to Roku products. But I may have moved on now.