OData permissions: GET succeeds but POST/PUT fail

Hi all

I have several OData services on my HANA instance (on HCP) where the following happens:

the OData service is very simple with just one or two entities, no forbidden instruction is defined.

Authentication has been set to SAML+Basic+Form, so almost everything is accepted.

The content-type is set to application/json and charset is specified to utf-8

Authentication headers are specified correctly

Payload is correctly formatted in JSON

But any call other than GET (e.g. POST/PUT) results in a 403 HTTP error.

I'm testing this through the Chrome Postman tool

Any idea why this happens?

Thanks

Vincenzo