I have recently installed Ubuntu 16.04 with dual boot in a PC with Windows 10. I was trying to connect it via HDMI to an external monitor, but it wasn't detected in Ubuntu partition. Searching at this page, I have found this answer and followed its steps. Now my problem is a little more awkward.
After rebooting and starting Ubuntu, now I can only display in external monitor. If I disconnect it then my PC remains with black screen and I can only use it in console mode (
F1). System Display options only detect a single screen and I haven't found a way to being able to display in PC screen. In Windows partition both screens still work fine.
How can I solve this problem? Or, at least, how can I go back to the previous state, when external monitor was not detected but PC screen worked fine? Thanks.