@Zacherous, it might still be possible, but I haven't played with any Vamps lately. I do have some Good Vampires but I've been playing more with new Sims I've made when I have gotten new packs (like Tiny Living, Eco Lifestyle, and Discover University). And I love to garden in my game so I usually have them eat plasma fruit since I have plenty on hand.
I did not see this on the Bug Report list, so please make a Bug Report on this so they can start to gather information in order to start fixing the bug! You can report this here: https://answers.ea.com/t5/Bug-Reports/bd-p/The-Sims-4-Bugs
After you fill out the Bug Report other people can click the "Me Too" button -- this is good so EA can see how big of a problem this is. Then people with the same problem can also add their experiences to the thread to further help EA figure out what is going on here.
Hopefully they can fix this so you can play your good Vampires again! 🤞
Also, I would reconsider and start reading the Vampire Lore books even If you are playing evil Vampires. There are a lot of tips, abilities, and drink recipes you can unlock , not just how to use frogs to make plasma packs.🙂. It is also good for your non-Vampire Sims to read so they can learn to make garlic braids, garlands, and wreaths to keep Vampire away, or learn drinks to cure them, etc. 😉