Billrv said

Using Win 10. Thunderbird had been working fine but I think there was a Win update. Icon on task bar shows thumbnail bit will not open the app. I can open my address book from the context menu or open a page to write an email ditto. Is working fine on my laptop, fortunately as I cannot get into my Inbox on my desktop. Thanks for any help.

I have since found how to open in Thunderbird SAFE MODE and the app now works OK. What can be deduced from this?

does it now work in all modes, or only safe mode?

If only safe mode, it is usually an add-on that has not made the transition through an update well. Or it couple be your anti virus side loading an add-on to manages spam or the like that really should not be installed at all.

Thanks for your reply Matt. It will not open unless I use safe mode. I can only get to this because I can open a "write new message" page from the context menu and then go to HELP. Strange thing it had worked fine right up until two days ago. I have used TB for years and never encountered anything like this before. Can you tell me how can I permanently disable add-ons?