Application.Match Run Time Error 13 in VBA Macro - vba

Question

This code was working about a month ago with out any issues.
The run time error (#13) points to:
lastRow = Application.Match(campus, subject.Range("A1:A35000"), 1) + 2
I have run the macro a few times with it being partially successful some times. Other times it does not get any data at all.
If the macro is partially successful, what would cause the type mismatch if the data in the columns is the same through out. All the data exported from SQL Tools and then copied and pasted to the worksheets.
Dim lastRow As Long
Dim firstRow As Long
Dim count As Long
Dim campus As String
Dim gradeCount As Integer
Dim current As String
Dim previous As String
campus = schools.Range("A" & i).Value
With subject.Range("A:A")
Set Rng = .Find(what:=campus, _
After:=.Cells(.Cells.count), _
LookIn:=xlValues, _
LookAt:=xlWhole, _
searchorder:=xlByRows, _
searchdirection:=xlNext, _
MatchCase:=False)
gradeCount = 0
firstRow = 0
If Not Rng Is Nothing Then
firstRow = Application.Match(campus, subject.Range("A1:A35000"), 0) + 2
lastRow = Application.Match(campus, subject.Range("A1:A35000"), 1) + 2
gs.Range("A" & rowCount).Value = schools.Range("A" & i).Value
gs.Range("C" & rowCount).Value = schools.Range("C" & i).Value
currentCampus = gs.Range("A" & rowCount).Value
current = ""
previous = ""
For count = firstRow To lastRow
If campus = subject.Range("A" & count).Value Then
current = subject.Range("C" & count)
gs.Range("A" & rowCount).Value = schools.Range("A" & i).Value
If current <> previous Then
gs.Range("C" & rowCount).Value = schools.Range("C" & i).Value
gs.Range("D" & rowCount).Value = grade
gs.Range("E" & rowCount).Value = current
previous = current
gradeCount = gradeCount + 1
rowCount = rowCount + 1
End If
End If
Next count
If gradeCount > 1 Then
gs.Range("D" & rowCount).Value = grade
gs.Range("E" & rowCount).Value = "*"
gs.Range("C" & rowCount).Value = schools.Range("C" & i).Value
rowCount = rowCount + 1
End If
End If
End With

Answer 1

This is an indication that the Match failed to find a value.
If the same formula occupied a worksheet cell, you would see:
#N/A