Hi,
Please check that if model is assigned to the service or not.
You can check it in SPRO > SAP Netweaver > Gateway service enablement > Backend OData channel > Service development for backend odata channel > Maintain service
Once you pass the technical service name and version, the next screen will show the service information and model information. Please check if model information section is filled or not.
If the model is not assigned, click on Assign Model and you will be able to assign the model to your service.
Regards,
Ekansh