I just performed a ramp test that my training plan had scheduled. After the ramp test, it said my FTP was 239 and asked me if I wanted to accept it, which I did. AI FTP prediction then says if I perform the next 15 workouts, I can expect my FTP to drop to 236. My question is: why include a ramp test in the plan and structure subsequent workouts based on its FTP value if AI prediction is going to ignore it anyway when it comes time to recalculate?
It’s not ignoring it, you’ll be training at a 239W FTP for the next 28 days. At that point you’ll get a new FTP, which as of now, TR thinks will be 236W. In 28 days if you’ve improved more than the prediction currently thinks, your FTP will be higher than 236, or if you get sick and miss a bunch of workouts it will likely be low.
TLDR: Your FTP will likely be different a month from now.
I’m still confused. If my FTP is 239 now, why would an extra month’s training be expected to drop it? It seems to be saying. I know you’re 239 now, but there’s not a training schedule we can give you where you won’t be worse at the end.
Why would TR build a program that will result in a lower ftp after following it?
Unless OP is drastically reducing volume that makes no sense.
And from what Jonathan posted recently, the prediction is based on a maximum and not a realistic ftp prediction. So the 236 prediction is your max 
Have you tried changing your plan at all? Increasing volume or intensity? Or is that just the first default suggestion? What’s your latest training history look like?
I get this from them to time.
As you do the workouts and rate them how the workout felt, some workouts during the 28 days will change.
Most likely the Prediction will change to positive as long as you stay consistent.
What does your plan look like? What type of workouts are you seeing?
I’d be happy to take a closer look. Can I share some of the details in this thread?
Welcome to the forum, by the way! 
Is that a TR plan? It looks like it is all endurance. I wouldn’t expect that to raise your ftp.
Of course your FTP is going to decline slightly because this plan consists entirely of easy endurance rides. It’s essentially like doing three consecutive recovery weeks without any build phases.
I don’t know what is your plan for 70.3, maybe you are saving yourself for hard running and swimming sessions.. but with this approach to cycling your a more or less on maintenance level.
Declining FTP while training seems like the opposite of the training goal. It must be issue with app logic…
There is no build phase in this training plan, just maintenance, so FTP will maintain or go slightly down. FTP can and in my experience will go down while training if there is no progression.
All of the yellow days are the problem here. They’re switching all of your workouts to endurance rides.
This is a result of the big jump in volume you currently have in place.
The best way forward would be to ramp up in volume rather than diving into the deep end of this higher-volume triathlon training.
There are ways to bypass Fatigue Detection, but I don’t typically recommend that, though it is an option if you’re confident that you can handle all of the training that’s on your calendar. It’s your plan at the end of the day!