I previously posted [[https://support.mozilla.org/en-US/questions/1493633|Can't launch Thunderbird on one Mac user account]] and the solution by @DavidGG worked then. But it isn't working this time. So I really need to know what file triggers the Thunderbird Install Helper dialog on macOS. Here are the steps for the current situation: Steps: 1. On user 2, launch Thunderbird. 2. Get the dialog that there's an update to 128.8.0esr. 3. Click the Restart to update button. 4. Get the dialog that there's an update to 128.8.0esr. 5. Click the Restart to update button. 6. Get the dialog to enter admin ID and password for installing the Thunderbird helper. 7. Enter the admin ID and password and click OK. Expected result: Thunderbird relaunches, now with 128.8.1esr. Actual result: Get the dialog to enter admin ID and password for installing the Thunderbird helper. 10. Log off user 2 and log on to user 1. Here is where I did something different from the previous issue. Last time I deleted Thunderbird and re-installed it. This time I did the upgrade. 11. On user 1, launch Thunderbird. 12. Get the dialog that there's an update to 128.8.0esr. 13. Click the Restart to update button. 14. Get the dialog that there's an update to 128.8.0esr. 15. Click the Restart to update button. 16. Get the dialog to enter admin ID and password for installing the Thunderbird helper. 17. Enter the admin ID and password and click OK. Expected and actual result: Thunderbird launches and I can use it normally. 18. Log out of user 1 and log into user 2. 19. Launch Thunderbird Expected result: Thunderbird launches and I can use it normally. Actual result: Get the dialog to enter admin ID and password for installing the Thunderbird helper. I'm guessing there's some manner of residual file that's preventing Thunderbird from launching on user 2. I've verified Thunderbird is in the system's Application folder and not in user 1's files. So I continued with the recommended remediation from the previous issue: 20. Trash ~/Library/Thunderbird 21. Launch Thunderbird Expected result: Thunderbird launches and I can proceed recover profiles.ini and the Profiles folder from the trash Actual result: Get the dialog to enter admin ID and password for installing the Thunderbird helper. How do I clear the pending install from user 2 so that Thunderbird will launch for user 2? What is the specific file or code line that triggers the request to install the helper? (Yes, I did move my files back out of the trash so I don't lose them. I also have a TimeMachine backup.) I suppose I could totally re-install Thunderbird like I did the other time, but I'm hoping for a less time-intensive solution. I guess I could also dust off my old programming skills and dive into the source code - an advantage of Open Source - but it's not a strength for me and Thunderbird is coded in a language I'm not fluent in.