Ok I figured it out.
Now it seems so obvious.
I have a custom Stranger setup in the levels and selected that in the Membership Options
then in the ‘Protected content page’ i told it to go to a Signup page,
but it won’t redirect there UNLESS you have the [subscriptionform] shortcode pasted on the page you’re trying to redirect to i.e. Signup.
Otherwise it defaults to the main page.
hope this helps someone else.
