After system update, my Epson Stylus SX 535WD was ''gone''. I tried in vain to add it as an IP printer (got the IP-address from the printer). The printer model is correctly recognized, software download starts -- but then the "software ... is not currently available..."
Resetting the printing system did not help. Downloading Epson Printer Drivers v2.15.1 from here
did not help either, downloading Epson Printer Drivers.
In the end, I re-installed the printer software from the original CDs. After that the printer showed up as a Bonjour Printer, and I could add it without problem.
But note: although the printer is installed now and working properly, I still get the old error message (...software ..not available...) if I try to add the printer as an IP printer !?