Not sure what you mean by "load my old Lightroom windows catalog"
All you have to do is copy the catalog file to a local disk (not the NAS) and double-click on it.
Why do you say not the NAS?
My Imac is not that big that it can content all of my pictures. Its for 14 years of pictures with sub maps sorted en named bij date, on each event. Therefore i have NAS. In the windows environment there was no problem. I can close and open each year. Developing the photo's on the windows PC The question mark disappeared when i pointed out -by example- to a 'moved' folder.
I have double clicked on the catalog placed on mmy Imac, you wrote and it started Lightroom and imported the catalog. But: The question marks remains on each folders again. Therefor i tried again. I chose one year and pointed oud tot the NAS. But nothing happend.