there is 'copy' and there is 'copy to clipboard' - if you are clicking 'copy to clipboard' nothing will happen. try clicking 'copy'

Nothing happens with either. Unfortunately

I suggest posting OS and version and Thunderbird version and maybe someone can advise. For me and win 11 and thunderbird 115.10.1, it works fine, there may be something else here. You might try in troubleshoot mode to see of any addons are preventing the copy.

I am using Thunderbird 115.10.1 version with Ubuntu 22.04 LTS. I have been using TB as long as 13-15 years I have never had this issue before. I believe during one or two recent updates something changed

using the flatpak version? I understand it has issues with copying because it is in a sandbox, but as I use neither that version or Linus that is all I know.

No it is not a Flatpak version. Only the original version that came with Ubuntu 22.04 It appears that this forum does not offer more in support.