Unfortunately we do not offer a guaranteed RESTful web interface for general access to GRANTA MI, only a SOAP interface.
The service layer does have a few little bits of RESTful interface, but these only cover a tiny area of MI capability while the SOAP interface covers the majority of MI functionality.
Please email support if you require further assistance.
If your problem relates to GRANTA MI please attach the MI:Viewer logs and MI:Server logs from the time the problem occurred (these are typically located in C:\\inetpub\\wwwroot\\MI\\logs and C:\\Program Files\\Granta\\GRANTA MI\\Server\\Logs respectively).