I’ve been dealing with the same problem. I’ve tried all the suggestions on Blizzard’s help page and it still hasn’t fixed it. /summonpet doesn’t work for other pets in my collection besides the white kitten, and if I right click the pet to “show in pet journal” I get a Lua error message.
I also got other pets to see if that would fix it, but it will just show that current pet in the journal when you select the message at the bottom once you’ve learned it. Eventually if I check the pet journal that learned pet’s profile is gone.