Importing from another catalog not working

I'm going to pull my hair out. In the past, I would export unedited folders from my main LR catalog to my Macbook and edit them while I am away. When I return home, I 'export as a catalog' my edited images to a flash drive. I then 'import from another catalog' to my iMac LR catalog. I've always done this in the past and never had any problems. My imported edited images would show up and the old settings would show up as virtual copies.

Lately, I followed this same workflow but no matter what I do, it doesn't work. I get as far as the 'Import from Catalog' dialog box showing the catalog contents but it won't let me check off the folder that I want to import. Also, it won't let me change the existing metadata and develop settings (grayed out) I have spent countless hours trying to do this every which way but nothing works. What has changed, or what am I doing wrong?  HELP!!

As an aside, I also in the past tried to follow Julienne Kost's method of plugging in my external hard drive into my Macbook and working on the images using Smart previews. That has never worked, which is why I just export and import the catalog folders. Anyway, I hope someone out there can enlighten me.

Thanks.