So, I bought MFS2020 for around a month ago. The download went smoothly, but for approximately 2 weeks ago I got a message saying that I was now using offline mode. There’s nothing wrong with my WiFi connection, Have over 150Mbps so that’s not the issue. Maybe the WiFi was was down for a couple of seconds, but it’s now working fine but I’m still in offline mode. Any ideas?

Same here. Did you find a solution?

Had the same problem, the system stated I had a network problem and switched me to offline mode. Check your setting under General > Data and make sure that - Bing data world graphics - is turned on. PS. Photogrammetry can also not be turned on without the above setting is ON.

I got this message once about low bandwidth.

As @pinepix62 mentioned, check your settings under General -> Data.  I found that they had been changed to 'OFF' when I received the message.  Turning them back to ON fixed things.