Help & troubleshooting for network issues, including connecting your device to your home Wi-Fi network, connecting to public networks, troubleshooting wireless issues & ethernet connections, and optimizing streaming performance.
What model Roku do you have? Model number, not just the name.
A blank screen and the network password are two unrelated issues. If you have the access to do so, just change the password to match your previous one. If you don't, then we have to figure out why you have a blank screen.
A blank screen is usually one of three things: the HDMI cable is bad, the HDMI port on the TV/Roku is bad or contaminated (dust bunnies) or the TV/Roku is defective. If the Roku was set to a screen resolution the TV doesn't support, the TV would usually display an error message. Test the Roku connected to a different HDMI port if possible, test it on a different TV, try a different HDMI cable. Make sure there's no dust buried in any of the HDMI connections.
Dan Roku Stick (3600), Ultra (4640), Ultra (4670), Ultra (4800), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.