Apple Mail doesn't display the signature dropdown in new email from line to select manual Signature
- Go to the Library folder of your user folder. It is hidden, so press command+shift+. to unhide all folders.
- Go to
Mail/V7/MailData/Signatures.
- Move the two .plists to your desktop
Restart your computer, open the application, and test. If it works okay, delete the plists from the desktop.