Hi Dave,
You have two security levels in the modeler. The Project Security of the roles you establish and the module security level. In your case, you need to allow access to the module security of the DataGathering Module for the entity DataEntry.
To accomplish this do the following, navigate to the entity DataEntry and open the properties:
Then navigate to the last tab "Access Rules", here you can give the user access to the specific attributes you wish, be it read, write or read only:
Here is some documentation to reference: https://docs.mendix.com/refguide/security
Hope this helps.
Thank you for the explanation and the answer, it worked for me too :)