Manager noted my employee file ineligible for rehire. With no reason as to why

I worked for a large company for 21 years. I had 2 children within the last 2years of working there after my 2nd child was born I resigned due to family. I followed all proper step. I was not fire and I didn't quit , and was told that if I wanted to come back, and if there was an open position I could apply. Now 5 years later job posted I applied and was told my employee file is noted ineligible for rehire by department manager. Now this manager was new only in my office 2 months and I was out on maturity. So he doent know me. During my 21 year all my evaluation were perfect. always received my raises and never exceed my sick time. My only long time out was my 2 pregnancies which where both under FMLA.