Logic Pro 10.4 lost project files

I haven’t used Logic Pro 10.4 for a bit more than a year. Now when I’ve attempted to use the program again, almost all of my saved project files (extension:   .logicx) show a size of “Zero bytes”, and when I attempt to open them, they show the error window saying: “The operation could not be completed. No other information is available about the problem.” The only change since the last time they worked was when I updated the computer to Mojave last year.