As far as I know, you may be from PC? I heard/read about to diconnect from web/WLAN, start Muse, reconnect to web.
Does this work for you?
Working on Mac, I did not have this issue so far, fortunately.
Your screenshot indicates to me that you're on a Mac. Which OS do you have?
Keeping in mind that Muse is End of Life and should not be used anymore, I'd say your Muse file is corrupted. Do you have a backup Muse file stored someplace?
Worst case scenario, download your remote server's HTML, CSS and JS files with Filezilla or Cyberduck. Use a code editor like Dreamweaver or Visual Studio code to make your site changes until you can rebuild your site without Muse.