Without having it in hand, it is difficult to troubleshoot. You may need to restart the device by pressing and holding the power key (if it has a power key on the model you own) (or) reboot the phone in safe mode (or as a last resort) back up and factory reset.

There may be several problems that cause this issue. Is there a graphics card? because when i experienced a similar issue, I shut down and unplugged the computer, carefully removed the graphic card and then reseated it, closed up and when I started up again everything was fine.

My dryer may be different from yours but i held the cancel button down for about 10 seconds. after that, the start button worked normally