Excel Application on Time Method Doesn't Work Properly

I would like to automatize scheduled report on my company. I found out a method called Application OnTime in Excel, which after some reading looks like a perfect match.

The task is following, on chosen periods during day I would like to import data through powerquery and then save a file. I would like to work it all the time. My simple code looks like that:

Private Sub Workbook_Open()
    Application.OnTime TimeValue("06:30:00"), "Module1.MyMacro"
    Application.OnTime TimeValue("09:30:00"), "Module1.MyMacro"
    Application.OnTime TimeValue("12:00:00"), "Module1.MyMacro"
    Application.OnTime TimeValue("14:29:00"), "Module1.MyMacro"
End Sub



Sub MyMacro()
ActiveWorkbook.RefreshAll
Application.Wait (Now + TimeValue("0:05:00"))
ActiveWorkbook.Save
End Sub

Due to overlong refresh of the data I gave extra 5 mins before saving file. However I encountered problem, after some time my script stops working. I have tried different solutions from the Internet, unfortunately I couldn't complete the task on my own.

I have a request If someone could tell me abaout what I've forgotten and explain the issue.