I did all the instructions correctly but screen Mirroring just doesn't work. I made sure screen Mirroring option is on "Always allow." But when I get to my Android phone, Roku 3 doesn't show up when I click cast. I'm using a Moto g6, so I'm not sure if that has to do with it.
Not all Android phones will cast to non-Chromecast devices, especially if, like Moto phones, have stock or near-stock Android. I have a G5+, and it also will not see any cast device (Roku or even myBD player.)
I have a moto e5 plus and after messing with it, found that its default Cast function works only with Chromecast devices. But you can download mirroring apps that will talk to Roku and other devices. My problem is that I can only get it to mirror videos that i have stored on my phone. I thought the whole idea of mirroring was to have it cast whatever is on my phone's display?