I am trying to save my document that I've put a lot of work into, but now it won't let me save it. I have tried saving it in various locations and names and get this same (attached) error. I have plenty of storage space on my laptop and am not using any external drives. I have tried simply creating a new file and copying the layers, but it still won't save the document. I am able to export the documents, which I have done, but I do not want to lose the source document.
Another interesting thing, I saw that it is somehow saving the document though it tells me it isn't. But, when I try to open it, it says it is already open. So, I tried to duplicate the document and save that, got the error about it couldn't be saved but noted that it still "saved" something to my desktop. So, I closed the duplicate file and tried to open the "saved" file and still got the error that the file was already open.
For reference, I am on a Macbook Air.