Cant update to 5.1.1 OTA

Hello , I have a sm g920f international version . About 10 days ago the terminal notify me an update to 5.1.1 but I was on vacation and did not actualize . When I got home I look for updates but it tells me that I have the latest version. Its 5.0.2 . Whats the problem with 5.1.1 OTA ?

Thanks