Sessions/Cookies not saving on Safari or Mobile when running from Heroku

I am running into a weird issue where when I run my server off heroku, certain browsers will not save the session or any cookies.

Everything works perfectly on my local, and when I go to my heroku site on google chrome or mozilla firefox on my mac AND windows laptop, it saves cookies as intended. However on safari on my mac, it does not save cookies.

No browser on my phone saves cookies. This is very confusing, and I have only seen one question relating to this, which was not exactly answered. Do you guys have any idea what might be happening?

The site is http://ift.tt/2lkHin1. I can send a link to github if it would help. Thanks for any help!