External Monitor Not Working

[deadbird11]

I am using Ubuntu 20.04 on a Dell XPS 13 9370 with an integrated Intel UHD Graphics 620 chip. Although my external monitor has worked for a couple months, it no longer does.

When I plug in the HDMI cable to my laptop, my laptop reacts as if the external monitor is working (I have the external display set as the main screen when two displays are in use, so my laptop has a "side view" of what's happening on the screen).
The external monitor itself is mostly dark, but will sometimes display what it is supposed to for a couple seconds if I plug/unplug the HDMI cable. Then, it is as if the monitor does not detect my laptop and the monitor waits for input for a couple seconds before going dark.

The Dell XPS 13 only has USB-C ports so I have to use a HDMI-USBC dongle. I have two of these and both have the same issues, so I don't think it's an issue with that. Also, my windows work laptop connects to this monitor with the same HDMI cable perfectly fine.

Any help is appreciated.

PS I am fairly new to linux

[ajgreeny]

Could be a cable breakdown problem; how old is the HDMI cable and was it a good quality cable when purchased new as they are prone to causing this sort of output problem?

Try another HDMI cable if you have one or can temporarily borrow one.

[deadbird11]

I think it's pretty new. I tried with a different cable and it was the exact same strange behavior.