Can't update FlightAware on my cell phone!

No matter what I try to do, I cannot get FlightAware to update on my iPhone 6S (T-Mobile). It always returns a “Request failed: Internal server error (500)” message or “Can’t sync to server” message. This happens, however, only when I am signed in! if i’m not signed in, I can delete or add airports, but only up to the 4-airport limit.