How to enable my macro on PPT? I keep receiving below message. "The macro cannot be found or has been disabled because of your Macro security settings."

How can I enable my macro on PPT? I keep receiving below message.
"The macro cannot be found or has been disabled because of your Macro security settings." 

All of my efforts for the past two hours failed!

- e.g., https://stackoverflow.com/questions/19712679/the-macro-cannot-be-found-or-has-been-disabled-because-of-your-macro-security-se

Thanks and much appreciated if I could solve this issue. 

c.f., I use Microsoft 365 Business version