Instagram login error

When I click on Instagram to check it when logging in, I get the following error:
{"code": 400, "error_type": "OAuthException", "error_message": "Redirect URI does not match registered redirect URI"}
The Instagram summary below the client information shows this:
Website URL www.website.com
Redirect URI www.website.com/index.php
So I cannot see the error. Suggestions?
The site is in a development directory online that is currently password protected until development is completed. Perhaps this is a problem, but I don't get this error from the other five login social site logins I've set up..

Yes, I did turn on "Use SSL for Authentication" and also the SClogin button is on the home page which is https://
I can't see anything wrong and yet I keep getting that error message.

Yes, I think that may be the problem. I'll also have to change the folder name again in the applications, once I'm ready to move the development site to its final folder in going live.