HDMI to Projectors not working on Mac Silicon (Intel works fine)

Hello Fourthlaw,

There are a couple of things we would check, all with the intention of isolating where the issue is coming from.

First, do you have another M Series Mac that you can test with. It would be helpful to know if the problem occurs with multiple M Series Macs.

We would also try another projector, if possible, to see if the projector itself has an issue.

After that, we would suggest starting up the system in what is called safe mode. Safe mode only loads what is needed to run the computer. This can help isolate what is causing issues.

To start in safe mode, follow these steps:

1. Turn on or restart your Mac, then immediately press and hold the Shift key as your Mac starts up.

2. Release the key when you see the login window, then log in to your Mac. 

3. You might be asked to log in again. On either the first or second login window, you should see ”Safe Boot” in the upper-right corner of the window.

More information is available here: How to use safe mode on your Mac - Apple Support

The computer will take longer to start in safe mode, and the screen may have some distorted video as it starts up. This is normal. Once you are logged in, use the system and test to see if the issue continues.

If everything seems to work as expected, go ahead and restart the computer normally and test again. There are steps outlined on what to do if the issue does or does not continue in safe mode.

Starting in safe mode also forces the computer to run some disk checks similar to First Aid. This can actually resolve some issues.

Have a good day.

what is the interface used by the device? {ThunderBolt, USB-C, HDMI, DVI, VGA, Composite-Video, Other}

what resolution?

how long are your interface cables to the device?

what model-year MacBook Pro and built-in screen size?

are you mirroring or extending the desktop?