Use the big blue square that says "+ New Message"

And if we don't see that displayed (in 115.3.3)?

If you don't see three dots at the top of the folder pane, then do View > Folders > Folder Pane Header.

If you do see three dots but don't see New Message, then click the three dots and click Show "New Message".

Did you have good results?

If you still need help please create a new topic. Locking this one which has gone stale with no responses.