HP 5600 All-In-One will not print

[Rgartner]

I recently connected this printer after being dormant for close to 1.5 years. It is correctly connected to the computer (appears in my active printers) and feeds paper when requesting a document be printed. However, the printer does not print anything on the paper. The cartridges slide across the paper like they should, but no ink comes out. We checked the cartridges, they both have ink (according both to what is on my hand and what's on the estimated ink levels screen).

Does anyone have any ideas as to why my printer is not printing properly?

[redcow]

If it's been in storage for a year, replace the cartridges.
The heads are clogged with dried ink.