“The user is currently already connected to a known proxy”

I have used the STARZ app for a couple years now by logging in through Cox Internet via various devices (Android TV, Amazon Fire TV).  Today I got the message “The user is currently already connected to a known proxy” when I tried to log on.  What does this mean?

I'm not even asking anyone to tell me what's wrong or how to fix the problem. Please just explain the error message.