Zoom share freezes and then won't let me share anything further

Image by PublicDomainPictures from Pixabay 

Dear Reader. This article has been composed over several weeks from 9/2/21. You might want to skip the bit in the middle and scroll straight to the end, to see that latest update and what I think is the solution to this problem. Please note that this article relates to Zoom running on Mac under macOS Big Sur.

Just recently, I have been encountering a new problem in Zoom - one that occurs when I am sharing a Powerpoint on my Mac, under macOS Big Sur.

The sharing of that Powerpoint freezes, with the meeting attendees no longer seeing the slides that I am stepping through - instead stuck on an earlier slide!

If I stop the share and try to re-share, the attendees just see a message that I am sharing, but no share screen appears.

In a class I was running early this week (the Files, Folders and Finder class that I was co-hosting for a local council), it happened within the first few minutes, and then occurred 2 times after that.

As a co-host, the only way that we seemed to be able to solve it was for me to leave the meeting and come back in to start the share again - something that is certainly not going to be an option going forward.

Today I experimented to see what I could do to get the sharing working again if the 'freeze' occurred, without me having to leave the meeting. Here's what I came up with to work around the problem.

I found that if I joined the meeting on another computer and made myself co-host, I could share a screen (even just the Whiteboard) from that computer - replacing the share that had frozen. 

Then, on the main computer, I could re-share the presentation without an issue.

During the very next class (the OneDrive Boot Camp​), I suffered multiple Powerpoint sharing freezes from early in the class. My strategy of using the second computer worked when this issue did occur, so I didn't have to re-start the meeting. Phew.

But I did find another way to get things going again - and that was by exiting the Powerpoint slideshow (which stopped the share), re-starting the slideshow, and then re-sharing. 

While this was frustrating, it was a fairly quick fix so did not hold up the class too much.

After the class, I did a bit more experimenting.

​The situation where it seemed to typically happen was when I had the Powerpoint in full screen mode, and was jumping from the presentation to another of my Mac's Desktops to demonstrate. (In saying this, it did also happen when I was just stepping through the full-screen slideshow.) It got me wondering if the problem is related to the 'full screen' mode and multiple Mac desktops.

So for my next Personal Technology Training (PTT) class (Ditch that scanner - great solutions for scanning that don't require a printer/scanner) today, I am not going to have my Powerpoint is full screen mode - and instead show it in 'window' mode. 

Fingers crossed. I'll let you know how this goes!

Update 10/2/21

We'll that theory didn't work. In yesterday's class, I had more freezes than ever and had to scramble to switch to my old MacBook (still running Catalina) and an older version of Zoom) to continue the class.

So now I am wondering if this is a Big Sur issue, given that the issue is not occurring Catalina.

I spent quite a while after the class yesterday testing out what might cause the issue. I managed to replicated it several times. Sometimes completely closing Powerpoint helped, but it was not clear what specific thing would 'unlock' the sharing to allow it to continue again.

I must say that I do have two displays in play during my Zoom classes, and my suspicion remains that the issue relates to Desktops.

In my final lot of tests yesterday, I reverted to a single display, and found the problem did not occur. So, for my next class, I will be trying the following:

• Re-booting my Mac before I start
• Ensuring I have any updates to Mac/Zoom installed
• Only running essential apps during the Zoom (to minimise CPU/memory use)
• Using a single display during the class Zoom.

And I will have my second Catalina MacBook ready to go if I encounter similar problems again. (Unfortunately, that MacBook doesn't have Windows on it as well, which limits what I can demonstrate during my classes.)

I'll report back on how all that goes!

If you too are suffering similar problems, please let me know in the comments below.

Update 24th Feb 2021

I have had mixed results with my Zoom sharing since writing the above a couple of weeks ago. Of the numerous classes I have run, I have only had two that allowed me to Screen Share without a problem - with late yesterday being the the most recent problem-free session.

I must say that for several of the sessions, I did not have time to re-boot and forgot about the single display! Silly me. So when the Share froze, I just reverted to my second Mac - which I have had at the ready for every session lately.

Yesterday, I re-started my MacBook before the Zoom class, made sure I didn't have other unnecessary apps running, and only used the single display (by closing the lid of my MacBook and just using my LG display, which as a camera for Zoom).

The other key thing I did was to pause syncing of Dropbox, OneDrive and Google Drive - something that I only did that one other time when the Sharing worked

So maybe that is the key to all this - preventing those other 'cloud' apps from taking up bandwidth when I am sharing? Seems strange though that my Catalina MacBook does not suffer similar issues.

I must say that the Catalina MacBook in connected via Wi-Fi, while the newer, higher-spec MacBook is connected via Ethernet. Surely that cannot be anything to do with it (?).

​I will let you know if and when I discover anything further.

On the question below on whether this impacts other platforms, I can't comment on this. As mentioned above, my problems are only being encountered under macOS Big Sur (as that is what I am using for my day-to-day Zoom meetings).

Update 3rd March 2021 - Success Finally

So, I think I have finally cracked it (famous last words!) - thanks to lots more Googling and two posts (one on Reddit, on on Twitter) that offered a suggested solution.

After starting countless Zoom meetings and starting sharing, I found that the freeze seems to happen about 3 minutes into the 'share', and then the share starts working again about 3 minutes later. From that point, it seems to work without a problem.

I have found a setting in Zoom that seems to fix this (for now).

It is the Use TCP connection for screen sharing, found under the Advanced option in the Screen Share settings. I now have this turn On - in the hope of a permanent solution to this Mac/Big Sur/Zoom issue.

I have tests this by starting new Zoom Meetings over and over with this setting on and off, and then shared a video with myself (on another device) shortly after starting each meeting. With this setting turned off, my share freezes every time. With it turned on, I could not re-produce the freezing issue.

Stay tuned again for news on whether this is the ultimate solution to this frustrating problem.

Update 4th March 2021 - It's still working

Today I ran a class that involved sharing a video for 30 minutes - and there were no freezes! Could this really be the solution?

Update 12th March 2021 - Still working!

This seems to be the solution. I have run several sessions since late update, and NO FREEZES! Let me know in the comments below if you have been having a similar problem, and if this solves the problem for you.