Out of Paper errors:
http://help.loftware.com/display/LPSKB/Zebra+printer+Error+Condition+Paper+Out+causes+and+solutions
PRINT CONFIG PAGE
PRINT IMAGE TEST PAGE
press & hold feed button until you see 6 GROUPS of green LED flashes. It will print a serious of black boxes to determine if their are bad spots on the print head.
\\gt-fs01\Company_Share\IT\zd420
ZD 420/421 Zebra drivers for RPRO