challenging a will

My elderly sister was in assisted living facility, in paramus nj and i was denied visitation and phone calls to my sister. my nephew has power of attorney.I am told by my nephew that my sister did not want to hear from me or see me. I believe this to be a complete lie. I also believe my nephew in my sisters incapacitated condition may hav coerced my sister to take me out of the will..Thank You . My email is jonathan_macanzie@aol.com