Please ensure that the hosted payments button is added to a web page, which is part of the domain/URL provided during merchant signup, as specified in the hosted payments developer documentation.

For example, if your website URL is http://myawesomestore.com the hosted payments button cannot be added to a web page different from that domain (http://notmyawesomestore.com)
   
The restriction was added as an extra security measure so the hosted payments button cannot be added to websites other than the merchant's approved/owned websites.