VBA cell assignments won't work? WHY?

this macro is hypothetically going to find the widest entry in each column, and then write that width in a new inserted top row. My problem is it doesn't like my cell assignments (even when they are exactly like cell assignments I've done in the past! any idea why it hates this line no matter how I program it?

        ActiveSheet.Cells(0, ccount) = 0
        ActiveSheet.Cells(0, ccount).Value = 0
        Cells(0, ccount) = 0
        Cells(0, ccount).Value = 0

Full code is this

Sub WidthCounter()
    Rows("1:1").Select
    Dim ccount As Integer
    ccount = Selection.Cells.SpecialCells(xlCellTypeConstants).Count
    MsgBox (ccount)
    Columns("A:A").Select
    Dim rcount As Integer
    rcount = Selection.Cells.SpecialCells(xlCellTypeConstants).Count
    MsgBox (rcount)
    ActiveCell.EntireRow.Insert
    rcount = rcount + 1
    
    For a_counter = 1 To ccount
        ActiveSheet.Cells(0, ccount) = 0 
        For b_counter = 2 To rcount
           temp = Len(Cells(rcount, ccount).Value)
           If (temp > Cells(0, ccount).Value) Then Cells(0, ccount).Value = temp
        Next b_counter
    Next a_counter

End Sub