Macbook pro use to let me close it and operate on external monitor. Now it won't.

[soundsystem00]

Because of serious desk space restrictions, I really need my laptop to be closed, but whenever I close it, I get an error saying basically the 60hz won't work with the monitor. I know it is a glitch because I have tried any different settings and it is always the same thing. Do you think sidecar could be causing this? Thanks.

 

[Dhock_Holiday]

How are you connecting the Macbook Pro to the external monitor? Are you using a cable or adapter? I had a similar issue with a Mac Mini, turns out it was the HDMI cable going bad. Something do with the leads in the connector separating from the housing. Replacing it with a new one fixed the problem.

 

[soundsystem00]

I am using an adapter and an hdmi cable. It is a reputable adapter and my PC works. The weird thing is, I connected my ipad to sidecar and was able to do it fine. Sidecar is making a glitch somehow.

 

[Fishrrman]

I don't know much about sidecar, but can it be "turned off"?
Or the existing settings set back to defaults?