XnView Software

I ran an import and sort. The folders appear to be created but none of the pictures were copied. Does anyone know if there is an existing bug fix or maybe I just didn't tick the right box?

Did you try to tick "New filename" option, and add {Filename} in the next field ?

I did. I have over 450gb of files. I have 10 folders in total I'm trying to import and sort. If I import one folder at a time with the subfolder yyyy/mm will the folder get overwritten each time I import one folder at a time or are the files just sorted to the existing folders.

During an import, no data or file should ever be lost - otherwise XnView would have a big problem.

I'm not familiar with the import tool but I'd say that XnView will move files to folders and create folders as required. If you repeat import several times, files will be added to existing folders while keeping existing files (given that filenames differ). That's what I'd expect XnView's import to work but as written above I'm not familiar with the import tool. If I were you I'd try with some few image files that you have backed-up before and then try it out. This way you are on the 100% safe side.