This is quite normal, and please don’t beat yourself up over it. I quit on my last ramp test. Not like you did, but I often quit when it steps up at minute 19:00. I knew I could have tried longer, but mentally I wasn’t in it. I hadn’t slept enough and I wasn’t feeling it that day.
Nevertheless, I at first accepted the new, lower FTP and only after easily acing the next few difficult workouts, I upped it to where it was previously.
Honestly, I think it is smart if you recognize the signs early and pull the plug early, too. A ramp test is supposed to gauge your current level of fitness. It is physically and especially mentally taxing, like all workouts where you have to go until exhaustion. (For the same reason workouts with 20±second sprints are extremely hard on me, whereas I can do 10-second sprints with ease.) So a test where you are just not in it is not going to give you an accurate measure of your fitness.
If I were you, I’d keep my FTP the same and see if I can finish the workouts. If I can, then I leave it where it is. If the workouts feel quite hard, I’d nudge down my FTP by a few %age points and see if that helps things. (Note that workouts shouldn’t be easy, a VO2max session should leave you panting at the end.) Or if the workouts are easy, well, then you up your FTP by a little. I feel with experience, I can tell whether or not my FTP is accurate within a few watts.