No alert at new message


we are using Spark as an intern way co communicate within our company. Suprisingly since this week I don’t get an alert when a new message oc my collegue arrives. Before that, I could minimize the window and at a new message the window popped up, or at least the icon showed activity.

What is wrong and where can I fix it? Right now I have to leave the window open all the time to get updates.

Thanks in advance and best wishes!