According to the link: https://www.instagram.com/developer/register/ I enter the phone number, description and link to the site: as soon as I have not tried it with http and https and without. Gives an error message:
Error saving your changes. The URL you entered is considered unsafe and may not be used.
With the highlighting of the Site field. What is the problem? Maybe this is due to updates and recent disruptions of the Instagram itself?