I have the Dell XPS 15 9570. I've had it since 2018 and have never had an issue with external monitors. All of a sudden, it has stopped working. I can assure you it is not the monitor or the HDMI cable because I have tested both and they are working fine. I tried connecting the laptop to another monitor and it would not work with that one either. I've tried reinstalling the graphics drivers and even reinstalled Windows 10 and it is still not working. I also used SupportAssist to scan for any issues and nothing has popped up. Any suggestions for next steps?