merge cells when command button clicked

Replace the maintenance button code with this.

Private Sub CommandButton3_Click()
Dim lRow   As Long
    Dim ws     As Worksheet
    If ComboBox1.ListIndex <> -1 Then
        Set ws = Worksheets(ComboBox1.Value)
    Else
        MsgBox "Please select an equipment."
        Exit Sub
    End If

    'find first empty row in database
    lRow = ws.Cells(Rows.Count, 2) _
           .End(xlUp).Offset(1, 0).Row

    'copy the data to the database
    With ws

        .Cells(lRow, 2).Value = Me.TextBox1.Value
        .Cells(lRow, 3).Value = "N.A"
        .Cells(lRow, 12).Value = Me.cboLO.Value
        .Cells(lRow, 13).Value = Me.cboSO.Value
        .Cells(lRow, 14).Value = "Weekly Maintenance"
        .Cells(lRow, 3).Resize(, 9).Merge
    End With
    Unload Me
    UserForm1.Show
End Sub

Just add these code:

    With ws

        .Cells(lRow, 2).Value = Me.TextBox1.Value
        .Cells(lRow, 3).Resize(, 9).Merge
        .Cells(lRow, 3).HorizontalAlignment = xlCenter
        .Cells(lRow, 3).Value = "N.A"
        .Cells(lRow, 12).Value = Me.cboLO.Value
        .Cells(lRow, 13).Value = Me.cboSO.Value
        .Cells(lRow, 14).Value = "Weekly Maintenance"
        
    End With