What kind of training have you been doing in the past 6 months since your previous test? Most people find it harder, at least initially, to make the same power indoors on a trainer as they can outdoors. A big fan helps but even with that the trainer feels different and takes a while to get used to.

Whether you do an 8 min or 20 min or 60 min FTP test, at the end of the day it's just a number used to provide guidance for your training workouts. It sounds like you haven't been doing many interval workouts. I would suggest you repeat the workout at a slightly lower power and see how that goes. If you keep them at the same power level you will end up dreading the workouts and skipping them.

I don't know what you're training for but it sounds like too much intensity at this time of year.