I have Roku Express 4K and tried to set it up on my tv but as sson as it starts after selecting the language there is a pop up for wireless network and it is just buffering and jo network not even my home network is visible on it and I am not able to go forward or back from here.
If you have a mobile hotspot available to you, try connecting to that to get through the setup/activation.
Otherwise, make sure you have plugged the Roku Express 4k device into the wall adapter, and try restarting both the Roku device and your Router (and any externals like modems, access points, extenders, etc).
If your device did not come with a wall adapter, use a USB charging adapter from a cell phone. (any 5volt, 1amp charging adapter will work).
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
Generally, if no networks are being detected, it usually means a failed/defective device. If you tried the above steps and still no networks being seen, then either return it to the store (if applicable), or seek a warranty replacement from Roku.