Oracle VPD issue

Just implemented VPD on an Oracle table to hide a column if the user is not part of a security group.

Have the function setup, package setup etc.

It seems to be working with a major glitch.

A user, who is not part of a security group, cannot read (select) on the column. expected.
A user, who is part of the security group, can read the column data. Also expected.

The issue is if the user, who is not part of the security group, cannot update the column via an application he is ning.
Same thing for a user who is part of the security group.

Any help with this is very much appreciated.

Thank you.