I received today my new television, a Toshiba 50U6863DB. I was able to set it up and connect it to my home Wi-Fi. It worked properly, including using it to stream YouTube and Netflix. I was able as well to connect it to my PC (Windows 10) through wireless display (Right click on desktop, Display setting, Connect to a wireless display and found and clicked on the TV that appeared on the list on the right) and I used it for a little while as a secondary monitor that mirrored my primary one. 

Unfortunately the TV screen, while mirroring my PC, was flickering and I started to fiddle with it to solve the issue; while doing so I attempted to change the monitor resolution from 1920 x 1200 (I think), the default, to that of my primary monitor that is 1920 x 1080. The TV and the PC screen both went black. 

After I restarted both the PC and the TV, Windows was again able to detect the TV but was not able to connect it any longer (when I try, the TV screen and PC monitor go black for a couple of seconds and after, they go back to normal and the PC says connection failed). After fiddling around more, I gave up and I reset the TV to factory setting, but not even that sorted the issue. 

How can I fix this?