Oh it's an array formula! ok try this one.
Formula: copy to clipboard 
=SUM(IF(MONTH(CELL("contents",INDIRECT("Quote Register!K13:K257")))=MONTH(Q$4),IF(YEAR(CELL("contents",INDIRECT("Quote Register!K13:K257")))=YEAR(Q$4),IF('Quote Register'!$L$13:$L$257=$B5,IF('Quote Register'!$E$13:$E$257=$D$2,'Quote Register'!$O$13:$O$257,IF($D$2="(ALL)",'Quote Register'!$O$13:$O$257,0)),0),0),0))