We can't send or receive messages

Hello,

For 2-3 weeks, irregularly, time to time, we can't sent or receive messages between us in the company. Sometimes, a person can send message to an individual but that person can't reply, basically "the tick" does not appear. We have a stable internet connection and updated version of MS Teams. Also there is this problem in the screenshot below. I'm curious about if there is something wrong with Teams' servers or are there another issue?

Thanks.