gfblack :
TheViper :
You may have a dynamic IP address on the printer which knocks it offline when the IP address updates.
Print out a Network Configuration Report from the printer. Should be an option directly on the printer. Check the IP address. If the last digit gets changed around after a few reports, that's likely the problem.
Right click your printer and select Printer Properties (not just Properties at the bottom). Click the Ports tab, select your printer and click Configure Port. Should allow you to lock in the IP from there.
HP1536dnf laserprinter off-line, had deleted and re-installed to get on-line.
Checked ip config under properties/ ports and found 'WSD' port selected. Changed to 192.16... standard tcp/ip and printer immediately began printing.
Thanks for your ip clue, you were absolutely correct!
Thank you TheViper and gfblack
TheViper as gfblack has said has pointed us in the direction of the problem (a dynamic IP address), how to evidence this (printing from the printer) and where in "printer properties" a port change will need to be made.
gfblack has added value by having us look for a selected "WSD" port and directed us to change that to a standard TCP/IP port.
I think that I can now express this advice as a single process that includes more detail about changing the port and getting the "instant printing" result. This will work in a W8 environment. Others may confirm whether it works for W7 as well.
1) Through the Control Panel, Hardware and Sound, Devices and Printers, right click on the problematic printer.
2) Select "printer properties", not properties. Select the "Ports" Tab. If the "WSD" is ticked, this is the port that you want to untick and replace. You are unlikely to be able to do this immediately.
3) Click on the "General" Tab. Click on the Administrator "Change Properties" button (this assumes you are logged on with Administrator rights".
4) Re-select the Ports Tab. Click on the "Add Port" button. A list of Available Port Types will displayed. If a "Standard TCP/IP Port" type is listed click on it, if not click on the "New Port" button, Regardless, each will launch the same Wizard that will allow you enter to an IP address and port name that will become static, When completed, click on the "Next" and "Apply" buttons. The "Standard TCP/IP Port" will be selected and the"WSD port" will be un-selected. Any jobs that are in the print queue will commence (i.e., you might want to delete some pending prints you may have accumulated along the way).