Membership: I want to recover a URL previously used y Protected Conent

I had both Membership and Protected Content installed. I have since removed Protected Content.

Protected Content used
Membership used

I deleted the "Register" page associated with Protected Content and cleared it from the bin

I'm trying to edit the permalink for Membership's registration page to:

When you browse to it redirects to

How can I get the URL to stay


Thank you in advance!