Digital Signature option is "stuck" can't send email in Outlook 20

I was poking around, trying to fix the problem that I cannot open the html
editor for a signature, when I mistakenly clicked on get digital signature.
All it did was open a new web browser, which I closed right away.

Now, when I try to send mail, I get the message "Outlook could not sign or
encrypt this message because you have no certificates which can be used to
send from the email address".

On the security tab, both on the email message and in Outlook proper, I do
not have any boxes checked.

Please help!