Collab broken for team members on Macs: "Cannot download entry"

Hey there,

We have a half dozen people working on a Collab project, and after a recent commit people who are using Macs can't get updates. We can see that there are updates available, but when we go to download them we just get the "Cannot download entry" error message.

The only solution I've seen suggested is deleting the Collab folder, which doesn't work. If you delete the project and go to re-download it, it won't let you and just gives the same error message. We also saw the problem might be related to Unity 2017.3, so we updated to Unity 2018, unlinked the project from Collab and re-linked it to a new project, and it's still not working.

Is there anything else we can try?