Why won't my phone sign into wifi?

[jakeataylorr]

Wifi at my school. I have the Note 4. When I had version 5.0.1 the wifi connected and didn't request a sign in. When I upgraded to 5.1.1 it asks me to sign in so I click the link, it takes me to my schools sign in page. I sign in, it disappears, but the sign in box doesn't go away in the drop-down menu. It stays connected for 3 minutes or so, then disconnects. It's like it never signs in. I don't get why it just now does this. Any help?