Hello Linda,
Thanks for that info and choosing the Apple Support Communities. I know how important getting your Lexmark all in one working with your Mac is to you!
Based on what you stated, it seems you may be having issues with scanning to your Mac. Because the printing and scanning work together, I suggest using these steps to get your Lexmark all in one working with your Mac again:
OS X El Capitan: Scanning troubleshooting
If you're able to successfully add the Lexmark to your Mac, then try starting a new scan from the Lexmark by using the Image Capture app on your Mac:
OS X El Capitan: Scan images or documents
Cheers!