Hard to tell without seeing  it. It could be there is a problem with a slip. If you print a small number of slips does it work? Will it show on the screen put not on printer? More information including version and exactly what you are doing would be helpful.

It is Timeslips 2018 and I am trying to print a Slip Listing from the Show Slips section.  It does show on the screen but when I go to Printer Setup and choose the printer, nothing happens. Thanks

Can you try going to reports - slips - slip listing and put in filters and see if you can print from there? 

Thanks, I can print from there. Is this the same report?  Maybe you just cant print from the other screen.

You should be able to get the same results from both places depending on filters.You should be able to print from either place but without looking I can't tell why it won't print so I am giving you a workaround. 

Sounds maybe like an issue with your printer.  Are you sure you are sending it to the right place?  Without seeing your screen I cannot be sure.