I have searched for an answer but nothing came back to this problem

I have a digital form to send to customers, which is time and download limited, I have set the attributes accordingly and everything seems to be in order.
When the test customer tries to download from their account, the page comes back with:

Forbidden

You don't have permission to access etc,etc,/test.zip on this server.

Can someone shead some light please?
Regards
Mike