The message in the attached screenshot "Unable to communicate with server. Saving is not possible at the moment" suggests a possible communication or networking issue which may resolve itself in time.  Unfortunately, this message is also produced when Confluence is unable to save a document due to the author having included an emoji in the page source.

A new or modified message to warn of the possibility of the presence of an emoji in the source would certainly help users solve the problem much more simply and directly.