Q: can't connect signature to Apple Mail

Unfortunately, I updated to El Capitan, and among other problems, the signature in my email suddenly stopped appearing. It's in the Mail preferences as Signature #1, is selected there, but when I open a new email, the little box at the right says "none" and the pull down menu only allows me to choose either "none" or "edit," The "edit' takes me back to the Mail preferences.

So how do I get my signature to start appearing again in new emails? It was working for the first few days after updating. It suddenly quit this evening.

i hope you can answer this as it's really annoying and causes a problem for professional mail that has to go out with my signature line.

Muriel