Whilst in the middle of printing, I accidentally touched the turn-off button on the printer & after that, nothing would print and the printer status in the System Settings/Printers for my ET-4500 showed as: “Stopped – Unable to add document to print job”.
I searched the printer menus, but could find nothing to help. It just wasn’t handshaking.
I deleted the printer and re-installed, selecting Network Printer and AppSocket/HP JetDirect. In the host field I typed the fixed IP address 192.168.m.n (m.n being the numbers I assigned in the printer settings). I clicked Forward and selected the test page option.