Run time error 1004. Method 'Range' object '_Global' _ failed

Question

When I run my program only for one line (instead of variable i, put any other number) of the worksheet, there's no problem. But when I tried to do it for other lines using a FOR loop, the error message appears Run time error 1004. Method 'Range' object '_Global' _ failed. The debugger always highlights the 14th line. But I don't know if I have to fix just this line. Hope anyone can help me...my code is below.

Sub depth()
    Dim VAR1 As Double
    Dim VAR2 As Double
    Dim VAR3 As Double
    Dim finalDepth As Double
    Dim i As Integer

  ' Calculation of depth when soil temperature is zero. Calculation 
  ' was made considering linear change of temperature between 2 values

    With ThisWorkbook.Worksheets("sheet1")
        For i = 2 To 30547

          ' (PART HIGHLIGHTED BY DEBUGGER)

            If Range("Fi").Value > 0 And _
                Range("Gi").Value > 0 And _
                Range("Hi").Value > 0 And _
                Range("Ii").Value > 0 And _
                Range("Ji").Value > 0 And _
                Range("Ki").Value > 0 And _
                Range("Li").Value > 0 And _
                Range("Mi").Value > 0 And _
                Range("Ni").Value > 0 And _
                Range("Oi").Value > 0 And _
                Range("Pi").Value > 0 Or _
                Range("Fi").Value < 0 And _
                Range("Gi").Value < 0 And _
                Range("Hi").Value < 0 And _
                Range("Ii").Value < 0 And _
                Range("Ji").Value < 0 And _
                Range("Ki").Value < 0 And _
                Range("Li").Value < 0 And _
                Range("Mi").Value < 0 And _
                Range("Ni").Value < 0 And _
                Range("Oi").Value < 0 And _
                Range("Pi").Value < 0 Then

                Range("Ri").Value = 0

          ' Calculation of depth when temperature is zero for each column on one row

            ElseIf (Range("Fi").Value > 0 And Range("Gi").Value < 0) Then
                VAR1 = (Range("Fi") - Range("Gi"))
                VAR2 = VAR1 / (Range("G1") - Range("F1"))
                VAR3 = Range("Fi") / VAR2
                finalDepth = Range("F1") + VAR3
                Range("Ri").Value = finalDepth

          ' Columns g and h

            ElseIf (Range("Gi").Value > 0 And Range("Hi").Value < 0) Then
                VAR1 = (Range("Gi") - Range("Hi"))
                VAR2 = VAR1 / (Range("H1") - Range("G1"))
                VAR3 = Range("Gi") / VAR2
                finalDepth = Range("G1") + VAR3
                Range("Ri").Value = finalDepth

          ' Columns h and i

            ElseIf (Range("Hi").Value > 0 And Range("Ii").Value < 0) Then
                VAR1 = (Range("Hi") - Range("Ii"))
                VAR2 = VAR1 / (Range("I1") - Range("H1"))
                VAR3 = Range("Hi") / VAR2
                finalDepth = Range("H1") + VAR3
                Range("Ri").Value = finalDepth

          ' Columns i and j

            ElseIf (Range("Ii").Value > 0 And Range("Ji").Value < 0) Then
                VAR1 = (Range("Ii") - Range("Ji"))
                VAR2 = VAR1 / (Range("J1") - Range("I1"))
                VAR3 = Range("Ii") / VAR2
                finalDepth = Range("I1") + VAR3
                Range("Ri").Value = finalDepth

          ' Columns j and k

            ElseIf (Range("Ji").Value > 0 And Range("Ki").Value < 0) Then
                VAR1 = (Range("Ji") - Range("Ki"))
                VAR2 = VAR1 / (Range("K1") - Range("J1"))
                VAR3 = Range("Ji") / VAR2
                finalDepth = Range("J1") + VAR3
                Range("Ri").Value = finalDepth

          ' Columns k and l

            ElseIf (Range("Ki").Value > 0 And Range("Li").Value < 0) Then
                VAR1 = (Range("Ki") - Range("Li"))
                VAR2 = VAR1 / (Range("L1") - Range("K1"))
                VAR3 = Range("Ki") / VAR2
                finalDepth = Range("K1") + VAR3
                Range("Ri").Value = finalDepth

          ' Columns l and m

            ElseIf (Range("Li").Value > 0 And Range("Mi").Value < 0) Then
                VAR1 = (Range("Li") - Range("Mi"))
                VAR2 = VAR1 / (Range("M1") - Range("L1"))
                VAR3 = Range("Li") / VAR2
                finalDepth = Range("L1") + VAR3
                Range("Ri").Value = finalDepth

          ' Columns m and n

            ElseIf (Range("Mi").Value > 0 And Range("Ni").Value < 0) Then
                VAR1 = (Range("Mi") - Range("Ni"))
                VAR2 = VAR1 / (Range("N1") - Range("M1"))
                VAR3 = Range("Mi") / VAR2
                finalDepth = Range("M1") + VAR3
                Range("Ri").Value = finalDepth

          ' Columns n and o

            ElseIf (Range("Ni").Value > 0 And Range("Oi").Value < 0) Then
                VAR1 = (Range("Ni") - Range("Oi"))
                VAR2 = VAR1 / (Range("O1") - Range("N1"))
                VAR3 = Range("Ni") / VAR2
                finalDepth = Range("N1") + VAR3
                Range("Ri").Value = finalDepth

          ' Column o and p

            ElseIf (Range("Oi").Value > 0 And Range("Pi").Value < 0) Then
                VAR1 = (Range("Oi") - Range("Pi"))
                VAR2 = VAR1 / (Range("P1") - Range("O1"))
                VAR3 = Range("Oi") / VAR2
                finalDepth = Range("O1") + VAR3
                Range("Ri").Value = finalDepth
            End If
        Next i
    End With
End Sub

Answer 1

You also need to add a period before all the Range calls

.Range("F" & i).Value