When I try to restore my lost bookmarks with the right JSON file, it doesn't work and I get a pop-up message that says "Unable to process the backup file." Why?

When the new firefox update installed, I lost my bookmarks. I tried to re load an HTML bookmark file, but it failed. Then I found where the bookmark JSON backups were and tried to load the most recent in, which failed. I even tried to copy a JSON bookmark file from my other computer and that didn't work either. Importing the HTML file always worked before What the frack happened to my bookmarks?