What could it be I’m doing that keeps the scale stuck?

I am 70 yrs old and have been overweight/dieting all my adult life. Here are the things I’m doing to promote weight loss:
No sugar/flour (90% of the time)
Intermittent fasting, 16-19 hrs
Very limited processed foods
Strength training 5 days/week, cardio 2-3 days/week

Here are some questions I asked:
Could it be…I am not active enough?
too much fat in lunch salads? (avocado, nuts, cheese, olives, dressing)
too big portions at dinner?
too much of an evening snack–usually fruit, nuts, a little granola

Suggestions as to how to approach? I feel like I’m missing something. At the same time, I have changed so much but not really lost any wt in the 3 mo I’ve been in Scholars. At a loss, and so tired of trying to figure this out. Thanks for your help!