u/mom-mom-mom-mom-mom

I used the Marquette method with no issues for a couple of years 7 years ago. Then I took a break and came back to it about 4 cycles ago. The fertility monitor has failed to catch my last two peaks (it just reads high straight through ovulation). I know because I also use a temp drop to track my temperature and I have clear shifts in my charts. I don't remember ever missing peaks 7 years ago. Is this normal? Do I need to look into another method? I want the peace of mind of Marquette as I get closer to menopause, but I don't want to go through most of a box of sticks only to get a bunch of highs because peak already passed.