One of the common problems is that users report that they get this error message.
You don't have Item Purchase Code or your Item Purchase Code is not valid.Please update your Item Purchase Code.
This can happen for the following reasons.
You have entered incorrect purchase code ( or it contains empty space ) in project_config.json
You didn't run the first step. The step to setup the project. ( Click on the link bellow )
Pls do "Setup your project" once again, and then do the "Deploy builder page". Refresh your builder page, and see if you get the error now.
If you still get the error, send us a ticket with this two files.