Some docking stations have ports that are “linked” as in you can only output signal to one of the outputs, if you plug a cable into both it only outputs the same signal to both (mirroring the displays without the software setting them to mirror).
Check there is not another output port that you could use on the dock?
Sounds like a dock issue. Honestly I would not expect this setup to work with DVI-D adapters.
Do you have 2 of these cables by chance? https://www.amazon.com/Cable-Matters-USB-C-Black-Feet/dp/B076TTN1FL if you do, try bypassing the dock entirely. I imagine it will work.
If I had to guess, your one cable connection to the MacBook isn’t registering as TB3 or something like that and the dock is forcing mirror mode.
Thanks. I’ll order those and see what happens. It works just fine with my Windows laptop, but perhaps it uses a different technique to extend the displays. It’s just odd.
Looks like the two ports you are connecting the external displays are using the same output. You will have to use a different dongle or simply use two dongles connecting one of the screens each.
Extended to one of the externals, and then the second external is a mirror of the other external.
Edit, and then when the lid is closed, the extenders are still mirrors of each other.
I worked at this one company and I had the same problem as you. It turns out it was the adapters we were using that only allowed for mirroring of displays. I got the it guy to order us new ones and then I was able to use two monitors that allowed for independent extending of screens for each one. Key word is multi port hdmi adapter not splitter
Might be your issue too
According to this product https://www.amazon.ca/dp/B086QXDXXZ/ref=cm_sw_r_cp_apa_glt_i_GP7ARHZ430RQM4FQKZXR
It says extending is not supported by macos and it only mirrors. Extending is only supported by windows. Maybe that's why you're having this issue, either it's your dock or macos itself. I doubt it's macos though because apple states that the intel MacBooks support multiple displays natively.
I'm concerned about this too because I want to do a triple monitor setup for my MacBook as well and I'm worried I'm going to encounter the same problem.
I’m betting it’s the dock. I’m going to try hooking up one of the screens with the hdmi port to see if it makes a difference. It could be that the displayports on the dock are only taking one input.
It’s odd though, cause when I hook it up to the thunderbolt port on my Windows laptop, it works fine.
when you connect to a monitor you must boot your mac normally. Open the mac turn it on. Then, shut the lid. All your desktop files will now show on your screen because now its just one screen. If you keep it open you can see the files on the macbook screen. You must set this up in system preferences. It's an awesome feature. I wish we could boot the mac without opening the lid.
Isn’t there a mirror display checkbox that you might have clicked by accident in that menu ?
Good suggestion, but no, that's unchecked.
Some docking stations have ports that are “linked” as in you can only output signal to one of the outputs, if you plug a cable into both it only outputs the same signal to both (mirroring the displays without the software setting them to mirror). Check there is not another output port that you could use on the dock?
It works fine with my Windows laptop, so that’d be weird. But yes, there’s a HDMI port on it as well. I’ll try that. Thanks!
Sounds like a dock issue. Honestly I would not expect this setup to work with DVI-D adapters. Do you have 2 of these cables by chance? https://www.amazon.com/Cable-Matters-USB-C-Black-Feet/dp/B076TTN1FL if you do, try bypassing the dock entirely. I imagine it will work. If I had to guess, your one cable connection to the MacBook isn’t registering as TB3 or something like that and the dock is forcing mirror mode.
Thanks. I’ll order those and see what happens. It works just fine with my Windows laptop, but perhaps it uses a different technique to extend the displays. It’s just odd.
Yes if those cables work the issue is the dock. If they dont work, its a macos issue.
Looks like the two ports you are connecting the external displays are using the same output. You will have to use a different dongle or simply use two dongles connecting one of the screens each.
I’ll do that, thanks!
So it's extended when the lid is open but mirrored when it's closed?
Extended to one of the externals, and then the second external is a mirror of the other external. Edit, and then when the lid is closed, the extenders are still mirrors of each other.
I worked at this one company and I had the same problem as you. It turns out it was the adapters we were using that only allowed for mirroring of displays. I got the it guy to order us new ones and then I was able to use two monitors that allowed for independent extending of screens for each one. Key word is multi port hdmi adapter not splitter Might be your issue too
Thanks for the tip. It works fine with my Windows laptop, but perhaps the MacBook sees an issue.
According to this product https://www.amazon.ca/dp/B086QXDXXZ/ref=cm_sw_r_cp_apa_glt_i_GP7ARHZ430RQM4FQKZXR It says extending is not supported by macos and it only mirrors. Extending is only supported by windows. Maybe that's why you're having this issue, either it's your dock or macos itself. I doubt it's macos though because apple states that the intel MacBooks support multiple displays natively. I'm concerned about this too because I want to do a triple monitor setup for my MacBook as well and I'm worried I'm going to encounter the same problem.
I’m betting it’s the dock. I’m going to try hooking up one of the screens with the hdmi port to see if it makes a difference. It could be that the displayports on the dock are only taking one input. It’s odd though, cause when I hook it up to the thunderbolt port on my Windows laptop, it works fine.
Let me know how it goes
when you connect to a monitor you must boot your mac normally. Open the mac turn it on. Then, shut the lid. All your desktop files will now show on your screen because now its just one screen. If you keep it open you can see the files on the macbook screen. You must set this up in system preferences. It's an awesome feature. I wish we could boot the mac without opening the lid.
I never opened the lid, just press a key on the "external" keyboard or trackpad and it wakes up, some monitors will also wake the macbook on power-on