iMac not recognizing my external monitor after I updated to Catalina 10.15.7
I have an iMac (21.5-inch, late 2013) with an Acer external monitor connected to it. The connecting cable is a USB 3.0 to HDMI.
Very happy with this setup and zero problems with it for many years. Until yesterday, when I updated the iMac's software to Catalina 10.15.7.
Now, the Acer monitor is a black screen that flashes the words "no signal."
If I go to my iMac's System prefs -> Displays and click "detect displays" nothing happens.
I tried resetting NVRAM. Also resetting SMC. (These were suggested steps I pulled off of a Google search.)
This is very disappointing. How do I get the use of my external monitor back, please?
iMac 21.5″, macOS 10.15