Blank external display M1 iMac

iMac 14M2LL/A

I just received a refurbished 24” M1 iMac yesterday and I used an Apple USB-C multi-port adapter and HDMI cable to connect a LG external display.  The computer sees the display and it is shown in the display preferences, but it’s blank.

I have used that same monitor with my 2017 MacBook air with no issues. (the display is only about 3 weeks old).

What I've done so far:

• Upgraded the iMac from OS 11 to 12.1, no help.
• Swapped HDMI cables, no help.
• Swapped USB-C multi-port adapters, no help.
• Swapped the USB-C ports on the iMac and the HDMI ports on the display, no help.
• Turned the display on and off and unplugged it and plugged it back in, no help.
• Re-booted the iMac, no help.
• Used the USB-C multi-port adapter to connect to a TV and the TV displays the desktop.
• Plugged the adapter into our 2019 MacBook air and the LG display worked.

Any suggestions?