"Warning! This app is not using HTTPS to securely obtain your permission."

[gravitas]

I am redirecting to

"https://www.fitbit.com/oauth2/authorize? ..."

but I still see this message when I reach the link above, why is this? 

[JeremiahFitbit · Accepted solution]

Because your application's redirect_uri is http, not https.

[gravitas]

So if I change the value from http to https it should remove that message? Even if my router will redirect https to http ? 

[JeremiahFitbit]

Yes, that would remove the warning message, but you really should use HTTPS to protect your users.