Femara/letrozole and possible late ovulation?

TTC for 2 years and usually have 25-32 Cycle days. I always have An ovulation surge and temp rise. Doctor prescribed femara and I did not ovulate by the 16 CD which was confirmed with ultrasound. My follicles only reached 14 mm and they needed to be at least 18mm. My temp never went up. No period yet. Then on CD 28 I had a temp surge but did not test for ovulation. Has this happened to anyone before? So confused. Wondering if I could have ovulated later?