error message when trying to sync to yahoo a/c

My yahoo a/c keeps getting a red error triangle with the message ’ connection failed ’ and continues to say possible cause is either temporary connection failure or incorrect settings . I have checked all the settings and they are correct. 

If I re install the a/c it works for a short time then starts getting the same message. I have a 2nd yahoo a/c which I don’t have any issues with. 

I am having the same problem with hughes.net mail.