Powershell fix not working suddenly after getting error code 12 issue in my save.

I've got a long running legacy family save that recently got error code 12 twice. It popped up the second time yesterday. I'd not gotten this problem before so didn't know how to fix it, so I googled it and went through a step by step suggestion. Copy a previous save, put it in a backup folder on desktop and name it 'backup'. I did it again, deleted the save that had 'bad' in it and tried to start it up today only for Powershell to suddenly give this message. I have no idea what caused it exactly, it had been working fine for a while. Has the save ruined my game? Is the save totally corrupt? Is Powershell broken? Is it my computer? I'm not sure where to start here.