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There isnt a scanner driver for El Capitan 10.11 for that scanner, the most recent driver is for yosemite 10.10.
We may be able to get this to work on your el capitan machine. Would you like me to connect and try to get this installed and working for you on screen, directly?
If so, I am sending you the offer now. Once that offer is accepted or rejected, we can continue.
Dustin S.Senior Technician and Network Switching Systems Operator / Maintainer.