Excel 2016 VBA on Mac - How to set a 'Form' Control Checkbox to 'True'

All, I'm new to the site and have been through numerous posts without finding an answer. I'm attempting to set the status of a 'Form Control' checkbox to "True" in Excel 2016 on a MAC. I keep getting a run-time error 438 and have tried multiple ways of calling the sheet, the workbook, and the checkboxes but none seem to work. Can anyone help?

Here is the code: (Sheet Name: Sheet1)

Sub SetCheckboxes()

ThisWorkbook.Sheets("Sheet1").Shapes("Check Box 66").OLEFormat.Object.Value = True

End Sub