save files disappearing

A few weeks ago I was playing on my legacy save I started during COVID. I’m currently on gen 8 and have poured hours into this save, making loads of houses and venues and sims. Last time I tried to play, I was unable to save afterwards, getting a few different error codes, so I closed without saving, knowing I would lose my progress from that session, but I hadn’t done much and didn’t mind restarting the day. I closed the game and left it. Today, I opened my game for the first time since to start a new save. I spent hours making a family and building a house, as per usual. I had finished most of the house when I decided to log off for the night and come back to it tomorrow. When I opened my saves to save, I noticed my legacy save is missing. I went to save this game so I could check on the main screen, but I got error code 21. So I hit “save and exit” and hoped for the best. It did not save, and I realised my legacy save is completely gone. I have an older, but less used, save that has been left untouched. Now I’m wondering where my legacy save has gone and how do I get it back? Also why have I been unable to save? I have tried resetting my console and left it unused for multiple weeks, but it hasn’t worked. I am reluctant to fully uninstall as I have most packs and it would take a very long time for everything to reinstall. Can I recover my legacy save? It is not at all on my main screen. Please help.