Cross origin error

[i3130002]

It appears to me that from three to four days ago the website has problems. Imagined it's me though I realized that this is not gonna solve by itself. Having the following error: Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://viska.herokuapp.com/socket.io/?EIO=3&transport=polling&t=N9V0PSm. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing). Please consider fixing it. With respect.