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The reference to P2 must be outside the quotes.
=SUMIFS(Labor!D:D, Labor!H:H, "<="&P2, Labor!H:H, ">="&P2-30, Labor!A:A,N2, Labor!K:K, "Time Worked")
In your description, you mention P2 should be greater than H - 30 and less than H. If that is your intention, the formula should be
=SUMIFS(Labor!D:D, Labor!H:H, ">="&P2, Labor!H:H, "<="&P2+30, Labor!A:A,N2, Labor!K:K, "Time Worked")