External monitor not working for Thunderbolt g2 dock with Macbook Air M1

[Joel_f1]

Hi,

I have a thunderbolt g2 dock, which I have used successfully with my Macbook Pro (Intel chip) for over a year. I recently bought a Macbook Air (M1 chip), and when I connect it to the dock, my monitor is blank. My keyboard and mouse work and I can see that the monitor is connected in the settings. But the monitor screen does not show anything.

I tried using a basic USB-C hub which worked successfully. I have also tried restarting everything, changing ports, a different monitor, to no avail.

Does anyone know why my monitor does not work with this configuration?

Thanks

[itsmyname]

@Joel_f1 -- does the monitor have multiple inputs (VGA? DVI? HDMI?). Have you configured the monitor to "listen" to one of those inputs? If you connect the monitor to a different computer (such as a notebook), and configure it to "listen" to the output from the other computer, does the monitor work?

[Joel_f1]

Hi @Itsmyname - Thanks for your response. I tried with two different monitors. One has VGA and 2 x HDMI inputs, I tried both HDMI inputs and confirmed that the setting was on the correct HDMI input number when I tried each of them. The other one has DVI and VGA inputs, I used the DVI input and confirmed the setting was correct on the monitor. In both cases, the monitor is detected in my computer display settings, but the screen is black.

Both monitors work as expected with my old Macbook Pro (Intel chip). 

Thanks

[itsmyname]

@Joel_f1 --  In both cases, the monitor is detected in my computer display settings, but the screen is black.

On your computer, under "Display Settings", select a  very-low resolution, namely 800-by-600, to see if sending that resolution to the monitor (by whatever cable) can cause the monitor to accept that "non-optimal" resolution.

Also, within "Display Settings", click the "Identify" button. It draws big numbers on each connected display.

Also, on your keyboard, hold-down the "Windows" key (near bottom-left of your keyboard) and tap the "P" key.  Choose "duplicate" to put the same video-output onto every screen that your computer has detected.