Hello everyone, I have no issue at home using Mac mini M1 with 2 monitors, one is direct to HDMI port, the smaller on uses USB C for its output and power. I can easily choose which screen to show my main mix output to when rehearsing at home. Recently i went to a pub/club and connected the M1 to their HDMI lead, and their projector and I could not swap over the arrangement in the usual way using Apple System prefs for Display, or the VDMX ‘go full screen’ option toggle either.
My desktop was always on the house projectors screen, so I could never work the back end in private on my mini screen.
IS there possibly a command key and special button configuration that will force it to change, or as suggested is it possible the club equipment is not HDMI 2 ?
previously when using MBP laptop in the same club, I easily switch me screen arrangement over so I can work.
I love using my M1 and when I used my own Optima projector at home, before I went to the club, I was able to choose the output using arrangement as normal in settings, to enjoy my set projected with a 4 year old projector.
Has anyone had this experience ?
thanks in advance
Did you drag the menu bar from the projector screen to your desired desktop in display preferences? That tells the mac, which screen is your main monitor.
easy with MBP , not the same when i brought my M1 along to the club
I’m not sure what you mean by that. The display preferences are universal across all Macs.
Sory if this isn’t the issue, but from the description (“My desktop was always on the house projectors screen”) it sounds like your main display was mirrored…? That you got the same content on all screens.
Whenever I’m connecting my macs to a new external screen they always defaults to mirroring the display on the new external screen. I always have to actively turn this off, to make macOS treat the new screen as an extension and not a mirror. It was unclear from your description if you had done this step, so it might be that.
How to do this depends on which macOS and how the display preferences panel are organized. Just google it for your version.
I’m using DisplayMenu which gives me a menubar shortcut to do this (plus it lists all the resolutions and frame rates that the Apple preferences hides).
http://displaymenu.milchimgemuesefach.de/index.html
Hope this helps
no not mirrored, I never use that display. ive been using macs for 28 years and its just in this club situation the M1 defaults to the room with their cables and projector
There are at least two separate issues at play, but both are related to external display connections. The problems appear to have started with the macOS Big Sur 11.2 update has not provided a fix and in some cases, has worsened the issue.
The first issue causes USB-C ports to fail to recognize external monitors, rendering external displays unusable and unable to connect. This appears to be affecting both DisplayPort and HDMI displays connected directly and through hubs and adapters.
I guess on this one Mac I will have to update to Monterey now… and go to the club ahead of the gig this saturday to test it
thanks for all the help, ill let you know how i get on 
Solved it - how to change Primary display (particularly on Mac mini with no screen ) between projector and my working VDMX backend - left click, hold on the screen within Arrangements of Apple OSX Preferences/Display - the small white bar along the top can be moved, I didnt know this, Ive often simply been able to swap between two screesn ( i. Never mirror ) … so I hope this helps anyone else maybe changing screens or HDMI cables and find their primary also change… Change YOUR macOS Primary Display on a Dual Screen Setup - YouTube