For centuries, people have not been able to agree on how to count the omer. As I understand it, the confusion lies in the verse Leviticus 23:15 "From the day after the Sabbath, the day you brought the sheaf of the wave offering, count off seven full weeks." The main point people disagree on is which Sabbath this verse is referring to....the 7th day Sabbath that occurs during the week of the Feast of Unleavened Bread OR the holiday sabbath (i.e., Nisan 15).
My family has gone back and forth each year trying to reconcile this but this year my son brought out a point that for some reason never caught our attention. In John 20:17, Yeshua cautioned Mary Magdalene to not hold onto Him because He had not yet returned to the Father. Then, Yeshua ascends to the Father with the perfect, eternal sacrificial body and assuming the role of High Priest, offers the wave sheaf of the firstfruits of the resurrection whom He had led captive (Eph. 4:10; Matt. 27:53; 1 Cor. 15:23). This must have occurred between the first day of the resurrection and a week later because John 20:26 states that Yeshua allowed Thomas to feel His scars.
So we are convinced as much as is possible or ascertained from scripture that the proper counting begins the day after the 7th day Sabbath occuring during the Passover week.