Hi there, I'm glad you like it so far!
If you're working off Firefox unfortunately something about the program at the moment doesn't seem to gel well with the saves. What usually works is saving your game manually which is done by clicking "save" -> "Save to disk" -> the file will usually go into your downloads folder but feel free to move it into its own folder -> then clicking "load from disk" and selecting it in your files to load the game back in. I'm trying to get everything working again but so far this is the only method that seems to work for firefox right now.
If this doesn't work for you, or you're using another browser please tell me so I can look into trying to get that fixed too.