Photoshop Files Locked on External Hard Drive

I just upgraded my OS to Mojave on my Mac Pro. So far things are fine. However, when backing up my files with Time Machine to any of my external hard drives I noticed that all of my Adobe files are now locked. If I double click to open them directly from the external hard drive Photoshop gives me the message, "Could not complete your request because the file is locked, you do not have necessary access permissions, or another program is using the file... etc."
If I drag any one of the copied files off of my external hard drive and back onto my desktop, I am then able to open the files. All of my "Sharing & Permissions" on my external hard drives are set to "Read & Write" and should allow me permission to open my backed up files. I have already contacted Apple as well as the external hard drive manufacturer, G-Technology. Both believe it may be an Adobe compatibility issue because it is only Adobe files that I am unable to open. Could it perhaps be the hard drive format on G-Technology's hard drive?
Please help. Thanks.