Re: Can't add any pets from the gallery
Hopefully someone will see this and it will fix it for them too - I was having the exact problem you describe and it absolutely was nothing to do with mods or files in my own game - It was a GALLERY ISSUE.
1. Anything that isn't properly downloading in CAS (for me it was All pets and some sims) DELETE your download of that family. That download is essentially broken.
2. Manually go to the creators profile of the family you want (hint: follow them before deleting from previous step to find them easily again) and download the family from there.
3. For me that was the issue solved.
I was absolutely tearing my hair out convinced it was my game, the fact I have 500+ active sim households, a few mods etc. All the galleries fault. It's been buggy from day one. Really hope this fixes it for someone else too.