When you use object of a schema to build HANA modeling views then it’s necessary to grant _SYS_REPO the SELECT WITH GRANT privilege on this schema. You need to execute the following:
GRANT SELECT ON SCHEMA "<SCHEMA_NAME>" TO _SYS_REPO WITH GRANT OPTION
To use tables from one Schema to create views we should provide access on the Schema to the default user who runs all the Views in HANA Modeling.
_SYS_REPO user is responsible for activating models and creating the required runtime objects from them. This is the reason you need to provide user _SYS_REPO to select objects in tables and views in the schema in the database. In case _SYS_REPO users cannot select the tables, views can’t be defined in HANA Modeling.