EMClient is taking ages (>50 minutes and still going) syncing messages but nothing has changed

Working OK until yesterday. This evening’s messages have not appeared in inbox and EMclient is synchronising messages in a folder that hasn’t been changed (and has been doing for 50 minutes - this folder has 3 small messages in it). Earlier today on startup it gave the ‘checking for errors’ box which is does every now and again, but it always fixes itself within 5 minutes.However this pm it took 20 mins.  Will leave on overnight, but concerned that it is bust/unuseable.