Some of the commands you could use (check the man pages for options)
lpstat
lpr
lpadmin
lpc
lpsched

You wrote that "At on time I could print from the unix machines "
I take it as "at one time" - So, what changed? I have UNIX systems that have been up for 616 days. The only time they break is when someone changes something (usually me, but I don't usually get caught either).