Lactate Threshold not auto updating

I have a F265S and a HRM Pro Plus chest strap. My understanding is the lactate threshold should update automatically with workouts but this hasn't updated at all. I run 5-6 times a week so would think it should have updated my threshold pace, just finished a 25km run with avg 4:49 pace, with the last 10km being 4:36 pace. Also ran a 15km a couple of weeks ago in 1:05:27 (4:22 pace). Surely that would mean by LT pace is closer to 4:22?