Access-Control-Allow-Origin header problem

[Mrsevic]

Did anyone encountered similar errror?

XMLHttpRequest cannot load https://simplewebrtc-eresult-server.herokuapp.com/socket.io/?EIO=3&transport=polling&t=1498057239863-5. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'https://simplewebrtc-integration.aerobatic.io' is therefore not allowed access. The response had HTTP status code 503.

[jakemco]

This usually happens when my server is down (and nginx returns 404s, therefore lacking the access control allow origin header)

[jamiegalbreath]

I also have this issue. works locally but not when pushed.