I am not able to link my Instagram to my Facebook.

I have an iPhone 5s and I am using the most current version on Instagram. I have been trying to link my Instagram to my Facebook because a week ago, all of a sudden I wasn't able to share images from Instagram to Facebook.

When I go to link the account, the Facebook login page appears, I enter my login information (I know I have been entering in the correct information) and when I tap on the "Login" button it is like the page resents to when I initially tried entering in my informatio.

I have uninstalled both the Facebook app and the Instagram app. I have removed the Instagram app from within my Facebook account hoping that would help. I have gone to my Settings>>Privacy>>Facebook and all there is is a slider button. Underneath that says "Applications that have requested access to you Facebook account will appear hear."

I have tried linking to my Twitter account and it links just fine.

I have also tried using a different email that I have under my Facebook (I have two emails linked to my Facebook account) and it still doesn't work.

I have looked everywhere else on how to manage this problem - Facebook, Instagram, Yahoo Answers - and I have found nothing that has done anything.

Please, someone help me.