Females will refuse a lock for various reasons. Does not mean that she won't lock next week. Have you tried palpating her (feeling for follicles)? I like to palpate throughout the breeding season because it gives me an idea of where my females are in regards to how close they are to ovulation or if they will go at all.

For example, I began breeding my normal female 11/14 (I'm pretty sure it was the 14th) and by 12/31 she had marble sized follicles. By 1/14, they had doubled in size. On 2/12 she ovulated. My pinstripe is a little more slow going. I began breeding her in December. I felt marble sized follicles on 3/28, and just today found these follicles had doubled in size. Palpating is useful. You should try it on your female and see if you feel anything. It might take you a few tries but if you can feel follicles and can guesstimate their size, you'll have a better idea of whether she will ovulate for you this year.