Final Cut Pro cannot save changes to “Untitled.”

"The storage location for one or more libraries is no longer available. The libraries will be closed so that no work is lost."

The above messages are all I get when I try to use Final Cut Pro. I'm a newer user. In another thread they suggested changing the name of the Library File, so I tried that (now called "Videos"), but that didn't do anything. Can't access any of my previous work, just get these error messages then the Library closes.