I can see app but can't open it

Hey, when I click on **inspect**, I get this error : 

> 403. That’s an error.
> 
> Your client does not have permission to get URL /serve_rev/@c0e649dc6b7990e24daaee45fc1682e006f4f0ca/inspector.html from this server. That’s all we know.


What's the problem?