I have the same problem in terms of having to Find. I hadn't changed any names or paths, but I couldn't get the images into my Project.
Using Find enabled me to select an individual image, but applying it to all the images in the folder, I'm asked to Merge.
This bit doesn't work. All the images are busy trying, but not getting there.
One of my other projects had the same issue. However, some other Projects do not have a problem.
Any pointers for what to look for would be appreciated.
I've tried renaming, reopening as defined earlier. I can Find on an individual level, but not for a whole folder.
Thanks. Colin