External Displays via Docking not working after latest update (10.15.6)

Hi, nialln71.

Welcome to the Apple Support Communities. We’re glad you decided to reach out about using your docking station and external display on your MacBook Pro. If we understand correctly, the display worked properly with the docking station before updating to macOS Catalina 10.15.6. 

If this is the case, try the steps outlined in “Check connections” here:  

Get help with video issues on external displays connected to your Mac - Apple Support

Notably, test by connecting the display video cable directly to your MacBook; disconnect and reconnect to reseat the connection; test with another port on your MacBook, etc. 

You might also check for any firmware updates that may be available for your docking station or display.

All our best.

nialln71,

Did you get a chance to check with the manufacturer of your docking station to see if there is software that may need to be updated? For example, some accessories (like J5, MTC, DisplayLink, etc.) may need to have the drivers refreshed. You can generally go to your Applications folder to see if you have software installed that corresponds with the name of your dock to check. 

It’s also a good idea to disconnect any other accessories. Some of our fellow users with this issue have had success with simply removing the Lightning cable they have connected to charge their iPhone. 

Let’s try this:

• Check for a potential software update from the manufacturer of your docking station, and install or update as needed.

• Disconnect everything from your MacBook Pro except the power adapter, and disconnect all cables and adapters from the docking station and each other.

• Reset the system management controller (SMC). Ultimately, we need to ensure that your MacBook is distributing the power that the station needs to power your externals. The SMC will reset the power flow.

How to reset the SMC of your Mac - Apple Support

• Reset the NVRAM. This governs the displays and resolution on your Mac. It may help.

Reset NVRAM or PRAM on your Mac - Apple Support

• When you reconnect the docking station, make sure you’re connecting to the strongest port, and don’t reconnect any other accessories. 

• When your displays and dock are all reconnected, power your MacBook on.

Any luck? If not, we suggest that you contact Apple Support for more advanced assistance.

Good luck.

<<Hopefully Apple will fix in future release?>>

These forums are great for brainstorming, and you have been fabulously lucky to be brainstorming with some of the best Apple employees, who have given you great advice so far.

But Apple Movers and Shakers do not make Engineering or Marketing decisions based on postings on these forums, only from systems submitted at the genius bar or from contact with Apple Support when a Bug Report is filed. There is no formal follow up from your discussions here.

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You do not seem to have mentioned, make&model docking station is this, anyway?

I have a similar issue. I have been using a Satechi Type-C Pro Hub Adapter for 2 years, with a direct HDMI monitor and a USB C to HDMI dongle (uni USB C to HDMI Cable), with both monitors working fine from the dongle. This adapter used both USB-Cs on a side of your MacBook. I then on the other side use an Apple HDMI / USB Dongle to supply power and the 3rd monitor. All was working great.

Since 10.15.6, I am unable to run the 2x HDMI via the Satechi dock, and I also upgraded to a caldigit ts3 plus, and with this I am unable to run 2x monitors going into the one connection it provides back to the Mac.

When I take the dongles and plug one monitor per dongle, per USB-C port, be it the CalDigit or the Satechi, I can only have 1 monitor in each port, but I can get all 3 running at once.

So, I can run 3x HDMI monitors if I have 1 dongle in its own Thunderbolt 3 port, but if you double up on a single port, this no longer works.

I thought the CalDigit was not powerful enough to run 2x monitors at once, but turns out it's 10.15.6. I dont have another Thunderbolt 3 Mac handy to test with on a lower version.

Sounds like a 10.15.6 issue to me.

I also encountered the same problem right after upgrading the OS to 10.15.6.

I have a 2019 MacBook Pro, 16 in.

I'm using an older LCD monitor with DVI output. It was connected via a Kensington dock with a DVI to DisplayPort adapter into the DisplayPort port on the dock. My intention was to be able to use two monitors with this dock. Before upgrading the OS, everything was working fine with OS version 10.15.5.

I called Apple several times but didn't get anywhere with them. So, I took my MacBook Pro and the Kensington dock to a local Apple authorized service provider. I asked them to check out the MacBook Pro and the dock and see if they could fix the issue or explain why it won't work. I picked up my MacBook Pro and dock today (8/24/2020).

I was told this is a "KNOWN" issue with the latest version (10.15.6) of Catalina. Unfortunately, the service provider said they had no remedy for me other than reverting my OS back to OS Mojave. But, I chose to stay with the current OS and work with the issue now that I know what's going on.

I was told to keep checking the support forum for news of when Apple fixes this. Who know's when that will be?

Before going to the local Apple service provider, I did a lot of troubleshooting. If anyone has any specific questions, I'll be glad to share more info.