Chosen Solution
External monitor is a Dell U2718Q. Message on the monitor says “No DP signal from device”. This worked pretty seamlessly for awhile, but it stopped working entirely. I’ve tried powering off both monitor and laptop, updated to latest MacOS, tried different USB-C ports on the laptop, different DP ports on the monitor, reset SMC, PRAM, NVRAM. Still doesn’t work. Any suggestions?
I haven’t tried other devices. I did find a workaround though: I have a TB3 - USB/USB-C/HDMI dongle. So plugging the monitor DisplayPort into the dongle via the DP/USB-C cable that I was using didn’t work. However, I then plugged monitor HDMI into the dongle, and it’s working seamlessly again. I think this suggests that the DP/USB-C cable maybe went bad.
