Code:
=COUNTIFS(Risks!$K:$K,">= " & $Y$3,Risks!$K:$K,"<" & $AA$3+1)
Code:
=COUNTIFS(Risks!$Q:$Q,">=" & 3,Risks!$Q:$Q,"<=" & 4,Risks!$K:$K,">= " & $Y$3,Risks!$K:$K,"<" & $AA$3+1)
You had a wrong reference for end of month. And the formula for start of month returned string instead of date, so no match was found. Replace the formula in Y3 with
Code:
=DATEVALUE(1 & " " & U3 & " 2018")