After spending hours getting nuts setting up my 7556 on my Mac, I have at last found the proper setting which always work.
This setup is for Mac OS 10.11, my Mac is precisely 10.11.5 yet it also worked on OS 10.10 (tested)
First you need to understand that there is an obvious bug in how the WorkCentre firmware (including the absolute latest after 3 altboot upgrades) would handle Bonjour and LPD protocol also configured as Multicast DNS Registration... IT DOES NOT WORK AT ALL... the only thing it would do is to advertise your printer when you try to install it and you would think you do everything right.
Until you print and then you get random errors like "Printer in use" or "remote host did not accept data file (32)" or "LDP Network Service not available, cycle power off and on"
SO FIRST DISABLE IT !!!!!! and reboot your printer
Also don't forget to set a Static IP address since you will not use Bonjour any more.
Ok so now you go back to your System Preferences/Printers and Scanners and click on + (after you have of course deleted all your previous unsuccesful attempts)
You will not see your printer advertised automatically as Bonjour is disabled... this is normal and logical !!!
Select IP Tab then enter the IP address of your printer manually (mine is 10.0.0.33), select Internet Printing Protocol - IPP
Your Mac should detect the printer and offer you to use the Generic PostScript Printer... Click on the drop down menu to "Select Software" then in the next window, search for your model and select it
Change the name and Location to something more friendly than the default IP Address.
And Voila !!!!! It works at last
My WorkCentre Firmware is
|System Software Version:|
MacOs 10.11 Driver version 3.68
MacOs 10.10 Driver version 3.65
WorkCentre 7525/7530/7535/7545/7556 Multifunction Color Printer
WorkCentre 7830/7835/7845/7855 Color Multifunction Printers
Enjoy your amazing printer again :-) !!!
Thank you so much for sharing this information. I know it will help a lot of people. I appreciate you taking the time to post!