Outlook emails intermittently not displaying on Macbook Air

I keep getting these messages when I log into outlook to get emails. Sometimes the emails show in my inbox but I can't view the content and sometimes nothing shows at all - I just get this message. Other times everything just works normally. I'm not very tech-savvy, so any suggestions would be gratefully received! This is just a recent problem - until a few weeks ago it all worked OK. I run all the Macbook updates when they are available.