VBA is turning off automatic workbook calculations

[mst3k4L]

Whenever I run this VBA code, the automatic workbook calculations are turned off, an d I have no idea why. Any ideas would be appreciated.

Sub solve_verror()
'
' solve_verror Macro
'
    Dim r As Long
    Dim i As Long
    Dim j As Long
    Dim LastRow
    Dim lastColumn
    Dim newColumns
    
    r = 24
    LastRow = Cells(Rows.Count, "A").End(xlUp).Row
    lastColumn = Cells(21, Columns.Count).End(xlToLeft).Column
    Range(Cells(r, 1), Cells(LastRow, lastColumn)).ClearContents
    
    'Inserts Required columns inside two V_leak summations
    tstep = Range("tstep")
    newColumns = Range("tinj") / tstep
    For j = 1 To (newColumns - 2)
        Columns("E:E").Insert Shift:=xlToLeft, CopyOrigin:=xlFormatFromLeftOrAbove
    Next
    Range(Cells(r - 1, 4), Cells(r - 1, 4)).AutoFill Destination:=Range(Cells(r - 1, 4), Cells(r - 1, 14)), Type:=xlFillDefault

    Do While Cells(r - 1, 1) < Range("tinj")
        Cells(r, 1) = Cells(r - 1, 1) + tstep
        Cells(19, r - 20) = Cells(r, 1)
        Cells(r, 2) = Cells(r, 1) * Range("q")
        Cells(r, 3) = Cells(r - 1, 3) + 1
        
        'Autofill has to include the original selected range
        Range(Cells(r - 1, 4), Cells(r - 1, 22)).AutoFill Destination:=Range(Cells(r - 1, 4), Cells(r, 22)), Type:=xlFillDefault
        Rows(20).Clear
        'Places variable on length row on top to match L_estimated column
        For i = 23 To LastRow
            Cells(20, i - 20).Formula = "=C" & i
        Next
        
        SolverOk SetCell:=Cells(r, 20), MaxMinVal:=3, ValueOf:="0", ByChange:=Cells(r, 3)
        SolverSolve UserFinish:=True
   
        SolverSolve (True)
        r = r + 1
    Loop
End Sub

 

[Warship]

maybe add this to the end?

Application.Calculation = xlCalculationAutomatic