Thunderbird will not open on iMac - the wheel of death keeps spinning on all areas of the window.

Does your issue resemble the one described in https://bugzilla.mozilla.org/show_bug.cgi?id=2060146 "Thunderbird hangs and is marked as Not responding while started on macOS, if Creative Cloud fonts are being retrieved."

I downloaded 'Rosetta' (an Apple app) a few minutes ago and then went to open Thunderbird and it has now opened successfully - I don't know if it was the solution or just coincidence!!

I don't know which macOS version you are running, neither which is your iMac model. If it is a recent iMac with the actual Tahoe 26 OS I wonder why you would need to install Rosetta. Current or recent versions of Thunderbird run natively on Apple silicon computers. https://support.mozilla.org/en-US/kb/thunderbird-rosetta-macos

Thank you for your responses Mapenzi - nothing was working when trying to open Thunderbird, the wheel was spinning in every part of the screen, couldn't do anything but force quit. I found a small window which asked if I wanted to open with Rosetta so with nothing to lose I ticked that box and lo & behold it opened the very next attempt. I had just updated on September 7 to the latest Mac OS Golden Gate 27 on an 18 month old iMac 24".

I've never had any trouble with Thunderbird or Firefox before, having used both for 10+ years now, previously on an HP using Microsoft.

PS: Best thing I did was to switch to Mac!! ;D

Thanks again - Brian