Custom Paper size

[charlotte w]

Hi, I have an A4 HP PSC 1510 all in one printer and I need to print a large document on the size 210mm x 594mm paper. Once I have set up the page size (canvas size) in photoshop and got the page ready to print I have changed the custom page size in page setup to my required paper size. When I go to print however, there is an exclamation mark that appears next the printer bar and it just will not print.

There are many people on my course able to print this page size on their standard A$ printers.. where am I going wrong?

Thanks