Hi Saini,
You need to set up the correct capability for the external entity from the application that is exposing the OData feed. to see if this is done the C in the CRUD needs to be purple to indicate that the capability is there , if this is done you need to make sure you are using the correct version of the OData service. just a heads up when committing the object , you need to use the activity Send External Object. you can read more here Write Data to Another App | Mendix Documentation