Lost my brush setting for signature in Elements 2023?

The easiest way is to simply copy and paste the symbol from a web page into a text layer.  You can even copy and paste this symbol:  © and you can get a reasonable result:

If you created the signature brush under the Default Brushes set, it should be at the bottom of the list, in the Brush tool dialog.

However, if you need to create a new one, you need it to be black on a white background.   Here is a sample signature that I created with the text tool. But you can even take a photo of your signature, as long as the image displays black on white.

Then simply go to Edit>Define Brush, give it a name in the pop-up dialog and click OK:

The black pixels of the image will now appear as a brush.