My Sign Up Form URL Is Taken

Once you've designed your Sign up form you have the option to edit the URL associated with it. At "Step 3: Share your sign up form," you'll be able to to edit the URL that your future recipients will see.>

If you click to edit the last part of the URL, enter your new ending, and receive a red “Not Available” message, this means another user has already claimed that URL and is using it for their own sign-up form.

Each sign-up form is unique and there can only be one sign-up form with a specific URL.  Try changing the URL to an even more unique ending.