Save.....failed

Hello, I’m a bit new to Halo and I’m having an issue with the campaign. It won’t allow me to save manually or automatically. It gives me the message “Save…failed”. I thought it might be related to my 5TB exterior hard drive, so I moved it back to the internal hard drive, but it didn’t work. Next I deleted it and reloaded it, but that didn’t work either. I know it’s a short campaign, but I’d rather not have to slog through the entire thing in one sitting. As near as I’ve been able to tell from talking to friends with the game nobody else seems to have this problem. Any advice would be welcome, thanks.