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Beta 8 External Monitor issue

Exact same issue here

MBP 2016 TB 15. Was connected to an LG 4K USB-C monitor. After installing beta 8, the display is blank and not detected,. I've also found that an external HDMI TV which was working is also now blank. SMC/NVRAM reset didn't help. Tried lots of plug/unplug to no avail.

I have another LG 4K USB-C monitor - plugged this in and it worked fine. MASSIVE RELIEF but still frustrating to get this.

I wonder if it's down to that monitor not being 'known' but being new.
Worst bug I've hit in this series....
 
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MBP 2016 TB 15 as well here. I have an LG ultra wide 34 inch monitor which does not work now. I have it connected via a usb c cable and tried a dongle with hdmi with no luck. Hopefully I will find a solution to get this working. A nasty bug indeed. I am even googling how to revert to a previous beta if there is a way!
 
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I'll add my voice to the chorus. 2016 MBP (Intel) and Dell external monitor via a thunderbolt dock. Tried hooking up my wife's display that I've never hooked to this Mack - same behaviour.

I submitted a Beta problem report, no response so far.
 
So - possible clue here. I followed an old post about USB-C monitors not working for 11.2, and did the trick of "Restart your mac and then close the lid" - and when it restarted, I see the apple logo and the login screen on the external monitor! Great, right? Not so fast. I type in my password, and after about 1/3 of the way on the progress bar - it stops. :(

I open the lid, and the system restarts, new login screen - interestingly new login screen and I can login OK - external monitor now frozen with the old hung login screen... cleared by unplug/replug.. now back to the black screen.

I see "Window Server quit unexpectedly" crash - which I assume related.

But in the end, still not working.
 
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Seems at this point limited to Intel Macs. I also had submitted a report to Apple yesterday and seems they already got several similar reports but no response or resolution yet as it seems. I guess at this point there is two choices, revert back to Beta 7 (if you have a backup) or wait and hope there is a Beta 9 next week that fixes it. But that means no external monitor till then …
 
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I commented on the other thread but I'll add one here too. Using a 2016 Macbook Pro 15", with a generic Amazon USB-C to Displayport adapter, to an Apple LED Cinema Monitor 24" MB382LL/A. Macbook's screen flashes when you unplug or plug in the USB-C connector, just like before, but only a faintly glowing blank screen on the external monitor. Display is not recognized in System Prefs - Display. Was working fine on Beta 7 but not on Beta 8.
 
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Everything go well with all the beta, except Beta8, all the USB-C, Thunderbolt or HDMI from MBPro (screen flashes) to the external monitor do not work at all.

Now, using AirPlay to 32" Samsung Monitor.
 
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Seems to be MacBook Pros only. I'm on a 2019 Mac Pro with a Gigabyte RX6800XT to an LG USB-C 4K monitor with no issues.

Lou
 
I have a 2016 13in MBP and have the issue. Tried a variety of things including swapping monitors and nothing has worked. I have 2 different USB-C dongles with HDMI ports and an external monitor will not work on either one after updating to Beta8.
 
flowrider said:
Seems to be MacBook Pros only. I'm on a 2019 Mac Pro with a Gigabyte RX6800XT to an LG USB-C 4K monitor with no issues.

Lou
Click to expand...
This second monitor problem exists on my Intel i7 iMac with a now dead 27" Apple Thunderbolt used-to-be-second screen.
 
thgoepel said:
Seems at this point limited to Intel Macs. I also had submitted a report to Apple yesterday and seems they already got several similar reports but no response or resolution yet as it seems. I guess at this point there is two choices, revert back to Beta 7 (if you have a backup) or wait and hope there is a Beta 9 next week that fixes it. But that means no external monitor till then …
Click to expand...
Lets wait for Beta 9 then, I'm using 32" Dual External Monitor setup and working from home, now, back to 13", its a pain in the ass.
 
I still don't understand why my LG 27UK850 IS working, yet my startech USB-C to HDMI + hdmi TV, & LG 27UD88 do not. All are 4K, USB-C devices.
- a difference in spec/usb-c in some way?
- the fact one hasn't been used previously on this install (saved state)?

Macbook Pro, 2016, Touchbar, 15", Intel

Last night I even disconnected the macbook to use elsewhere, plugged it back in just now and the ext monitor is still working great....
 
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Not seeing this problem with my 2015 MBP Retina / Dell 2415Q combo.

Footnote - using HDMI connection..
 
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It is listed in the known issue in the release note when I tried to report the beta bug. It suggested to use the original adaptor. However, I did so and it does not help...

Oops, need to wait for Beta 9 to see if the external monitor will be back.

I hope I should have read it before I install this beta.:(

1632991075057.png
 
I noticed the LCD should be detected, yet the communication should be in trouble. The monitor's LED indicates a connection is there as the discrete graphic card is switched to, just simply the display is not established. I also filed a new report.
 
chriswu@twn said:
It is listed in the known issue in the release note when I tried to report the beta bug. It suggested to use the original adaptor. However, I did so and it does not help...

Oops, need to wait for Beta 9 to see if the external monitor will be back.

I hope I should have read it before I install this beta.:(
Click to expand...
I don't think its related to that, I am using the original power adapter here and the original usb-c to display port adapter.
 
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Problem is on iMac (2016) too using Apple Thunderbolt 27" additional display.
 
ZoranP said:
Problem is on iMac (2016) too using Apple Thunderbolt 27" additional display.
Click to expand...
yup.. same here on a late 2015 iMac 27.. AMD Radeon R9 M395 2 GB .. via TB to display port .. Lenovo t24h.
Display obviously gets an activation impulse, but stays dark / undetected..
(report was filed.)
 
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