You can try running a few diagnostics. Most of these can be done by, eg, going to Control Panel/Printers, selecting the relevant printer, and hopefully there it will say what options there are to check how the printer is doing and what you can do about it.
First guess is to check if the nozzles need cleaning -- I think this will be possible to check without too much difficulty by following the on-screen instructions from the above point, but if you are still not able to sort it out then I can do some more detailed research.