Came here to report this, too. You are not alone.

After updating to v.140.0esr from v.128esr, I cannot compose a new message in my main virtual inbox. The +New Message button is there, but clicking it does nothing. I was working for over a decade before.

However, going into the normal NON-virtual account folder inbox still allows me to click the "+New Message" button and start/compose a new message.

For me, on very brief testing, it appears it is an issue with virtual folders. The Virtual Folder feature of Thunderbird is to me the MOST important feature of this email client.

Can anyone confirm that it is NOT working on virtual, but IS working on the normal inboxes?

The New Message button works here with Unified View in 140/W11. Try resetting virtual folders and see if the problem persists.

https://support.mozilla.org/en-US/questions/1429758

Update: Actually, the "+New Message" button does not work on any Local Folders, only under actual account folders in the left side tree.

Edit: When I create a new folder under Local Folders, clicking New Message still does nothing while in that new folder.

But if I move that new folder to an existing email account, then go to the new folder, clicking New Message works correctly.

Edit 2: 2025/07/10 I keep trying to post a reply with a lot of this info, but it doesn't seem to show up.

Edit 3: I am not sure why I am being blocked. I have the info you asked for.

Check Error Console (ctrl+shift+J) for errors

If it reproduces in Help > Troubleshoot mode ... Specify if it happens with Unified, normal or only local folders

Post here details here and also file a bug report https://bugzilla.mozilla.org/enter_bug.cgi?product=thunderbird

Thanks

Thanks for any help anyone can provide!

1) I have not received email notifications when anyone replies to this so I am doing my best to periodically come back and check.

2) Like the OP, Help > Troubleshoot mode with no addons made no difference. I still had the problem, which surprised me.

3) It happens in Unified and all the local folders I have tried, but I am not sure what "normal" means. If it is my actual email account folders, those work fine.

4) Note that I CAN reply to messages in my local and Unified folders, just not start a new message.

5) I ran the Check Error Console. Here is the paste:

1752107893534 addons.xpi WARN Checking C:\Program Files\Mozilla Thunderbird\distribution\extensions for addons This page is in Quirks Mode. Page layout may be impacted. For Standards Mode use “”. background.html WebExtensions: Import modules with new 'ChromeUtils.importESModule' implementation.js:34 Hello there, I'm BorderColors-D! background.js:11:9 CopySent2Current: 3.39 on Thunderbird 140.0 Received: pong

1.0.9 background.js:141:33 no migration CardBookXULNotifyListener.js:600:13 TypeError: can't access property "document", currentWindow is null implementation.js:568:15 1752107894980 addons.webextension.{a300a000-5e21-4ee0-a115-9ec8f4eaa92b} WARN Loading extension '{a300a000-5e21-4ee0-a115-9ec8f4eaa92b}': Reading manifest: Warning processing locales: An unexpected property was found in the WebExtension manifest. 1752107894980 addons.webextension.{a300a000-5e21-4ee0-a115-9ec8f4eaa92b} WARN Loading extension '{a300a000-5e21-4ee0-a115-9ec8f4eaa92b}': Reading manifest: Warning processing chrome_injectors: An unexpected property was found in the WebExtension manifest. New compose tab 5 with identity id1 styleswitcher.js:31:15 Applying new border style for identity id1 to tab 5 styleswitcher.js:45:13 New compose tab 6 with identity id1 styleswitcher.js:31:15 Applying new border style for identity id1 to tab 6

See https://bugzilla.mozilla.org/show_bug.cgi?id=1976624

Please provide feedback there.

Since they let me back in this place, I will copy over the solution from that bugzilla thread that worked for me:

You have to set an account as the "default" account.

Go to Account Settings Pick which one should be your main account On the top of it's page choose: Set as Default

Now my +New Message button works again!

Thanks everyone!