I have just upgraded a Lenovo T420 from Windows 8.1 to Windows 10.
After the upgrade I performed a "Reset this PC" with "Keep my files".
Periodically the wi-fi will die. No networks will appear in the list in the pane which appears when one clicks the icon at the bottom right.
The fastest way to fix it is to click the left-most button twice, which seems to disable/re-enable and automatically reconnect to the network.
I have checked the router. The problem is not manifesting on another Lenovo laptop upgraded the same way. I am using the latest available network driver.
So far I haven't performed a clean install due to the time it will take to copy files from the machine and back again (it would be great if "Reset this PC" allowed one to "Remove everything" except folders in the root of the PC, or specific "safe" folders).
What can I do to further track & resolve this issue?