Same problem. Device worked great for a year or so. I reviewed as many answers as I could. Everything seems to be set up properly. After a week of so of restarting the Roku, I discovered that every time it wouldn't connect, rather than restarting, I did this:
Settings > Network > About > Check Connection
It's been about 2 weeks & has worked every time I've run the Check Connection. Simplest answer I've found as restarting is a pain. This is just less of a pain. I'm convinced this is a Roku issue as all my other WiFi connected devices connect without jumping through hoops. I'd happily buy an ethernet cable if the Premiere had a port.
BTW, I have a 10 year old Roku 3 connected to a different TV that has given me very little trouble. OTOH, it' cost about $100.
Did you verify that your 2.4ghz band is configured to use b/g/n Wireless Mode/protocol at your router if you are using a cable ISP (Xfinity/Comcast, Cox, or AT&T)?
If the above is not applicable, perhaps try changing the wireless channel on the 2.4ghz band (1, 6, or 11 preferred) and try lowering the Bandwidth/Channel Width to 20 Mhz if you currently have set to 40 Mhz.
Did you verify that your 2.4ghz band is configured to use b/g/n Wireless Mode/protocol at your router if you are using a cable ISP (Xfinity/Comcast, Cox, or AT&T)?
If the above is not applicable, perhaps try changing the wireless channel on the 2.4ghz band (1, 6, or 11 preferred) and try lowering the Bandwidth/Channel Width to 20 Mhz if you currently have set to 40 Mhz.