Hi Marcy, Glad that Klinger is eating for you and seems to be feeling better.
In my experience with Harley, FortiFlora can be hard on the GI tract because of the animal digest used to give it that yummy dry food taste that cats can't resist. I used it with Harley after his first pancreatitis attack to get him to eat and he seemed to get better for a week and then he got worse and had his much more severe attack complete with severe vomiting. I'm not saying the FortiFlora caused the second attack because correlation is not causation, but it's possible that it was a contributing factor because Harley also has IBD and not all IBD kitties can tolerate animal digests. Since then, I learned from the Yahoo Pancreatitis and IBD lists that Harley wasn't alone, other kitties had difficulty in tolerating FortiFlora. Just something to bear in mind. If Klinger refuses the food with FortiFlora in it, he may not like the taste, or he's remembering that it made him feel bad. And if he does eat it and throws it up again, I'd recommend discontinuing it and see if he still has tummy issues.
Wishing you guys a Merry Christmas!