Some users who have experienced this problem and tried to come up with a workaround report that downloading Slack from its official site resolves the problem and is one way to bypass the error message and use the app normally.
Some users have tried reinstalling the same App Store version to no avail – the error keeps occurring. This is because simply uninstalling Slack doesn’t get rid of the user-specific data for the app, which is what seems to be at the root of the problem.
Manually fixing the problem
If you are interested, there may actually be a third way to use Slack without getting the annoying error message and below we will show you how you can do that:
- Uninstall Slack
- Delete all files related to Slack from your Mac. Find and delete all Slack files that would otherwise be left behind after the app is uninstalled. Additional file leftovers may be left at these locations
Locations on Mac
- ~/Library/Application Support
Slack File Names
3. Now, download Slack from the App Store and wait for it to get installed on your Mac.
4. Once you try to open the app, you will have to re-enter your login details. Inside Slack, all your previous settings should now be deleted and this should allow you to run the app normally.