I get an error returned that reads:
[error] => Unauthorized operation - please use a valid token with the required permissions. Reason scope required purchase:verify [response_code] => 403
It appears my personal token is good but it doesn’t have the correct permission.
The permissions for that code are:
This token has access to:
View and search Envato sites
Verify purchases of your items
I think you are using the wrong API method to validate a purchase code.
Here is an example of how to accomplish correctly this verification (click the link to view the code formatted):