How do you enable cookies with the newest IOS?
Taken from https://gaming.stackexchange.com/q/278248/105931


  Here's what I did that worked for me. Might not even need to do what I did...
  
  
  Iphone > Settings > Safari > Block Cookies > Always Allow
  Open Safari > Gmail.com > Logon with your gmail account > Open
  Pokemon Go
  
  
  More information about this issue from niantic itself