There's a chance that there may be a problem with your current connection.
A good tip is to try creating a new connection with your same account. You can do this by opening your main library --> tap the orange plus sign in the bottom right --> tap Add Storage > tap Add (choose your connection).
You'll now see two icons for your connection, and the issue may be resolved with the second connection. You can then delete to old connection.
If you receive an error trying to save a file that says to check internet connection, but you know you are connected to the internet then please refer to this article. https://help.folia.com/knowledge/my-file-wont-save-and-the-app-says-to-check-my-internet-connection.-what-do-i-do