Trying to export files, Error says they can't open?

Ok so I am using my new Macbook and it is logged into my iCloud on my account. This computer is shared among other users. I go on the app Pixelmator and photoshop a photo. When I try to export it, it gives me an error that states: untitled.pxm cannot be opened. I couldn't even save the file until i changed the location to iCloud Drive. It still wouldn't let me export it. The other day, I had edited a picture and it worked smoothly. I exported it and saved it no problem. I thought it was just the application. Then when I tried to export a keynote, the same error happened: untitled.key cannot be opened. I had to change the location to save again but still couldn't export. I am not sure if it is because of iCloud or because of my computer, but I searched everywhere on the internet and nobody seems to be having the same problem. I am not sure if it happens on the other accounts on the computer, and my wifi is pretty strong. I don't know what it could possibly be! Same thing happened when I tried to open a Pages document from iCloud Drive. The same error message popped up. Can someone please help?