I've started a new thread here for the issue in 2024 but if you look back this issue arose in 2020, 2021, 2022. It is probably the most catastrophic bug you can run into and I'm stunned that something this significant can still happen. After hours of work today I could not get my file to save no matter what I tried.
I tried save, save as, save incremental. Nothing. I tried exporting to old formats, no good. I tried collecting files, nothing. I tried saving to different folders, tried saving to different names, saving to desktop, nothing. Tried checking auto-save -- nope, just the original file. I tried exporting to XML, nothing. I cleared cache, tried to trash preferences, still couldn't save.
I would have tried a workaround some folks suggested of sending the comp to media encoder and then finding the temp project in the media encoder folder, except I couldn't get anything to export to media encoder either. (Which is a separate if connected issue I'm also having.)
I have no solves to offer, the work is lost, so it goes.
I uninstalled AE and reinstalled and it's working appropriately now,