Subscriber role-Oops! You do not have sufficient permissions to access this page

DP 6.6.3 & WP 4.0

Hi,
We are using DT as a membership-only site.
Every listing have restricted access and as such only paying members are able to access them.

Once they become members, they are allowed to access listings. Inside every listing there is a form. They fill up the form and send Submit.

The issue we are having is that when members fill out the form and hit Submit, the system just says:

“Oops! You do not have sufficient permissions to access this page.”

Only the admin is able to Submit without issues.

Any help will be much appreciated.
Thanks!