Why do people try to pray on people for healing and nothing happens?
Have you been baptized by the holy spirit? Not baptized only by water but by the fire of God and FILLED and baptized in your spirit for the work of ministry? On the day of Pentecost in Acts 2, the disciples were baptized by the fire of God. filled with the holy spirit and were speaking in unknown tongues from the spirit of God.
There is water baptism
And this water symbolizes baptism that now saves you also—not the removal of dirt from the body but the pledge of a clear conscience toward God. It saves you by the resurrection of Jesus Christ.1 Peter 3:21
Jesus answered, “Very truly I tell you, no one can enter the kingdom of God unless they are born of water and the Spirit.”John 3:5
Aside from being baptized by water,
2.There is the baptism of the new birth (when you are born again and become a christian) Galations 3:26-27
He saved us, not because of righteous things we had done, but because of his mercy. He saved us through the washing of rebirth and renewal by the Holy Spirit.Titus 3:5
Paul said, “John’s baptism was a baptism of repentance. He told the people to believe in the one coming after him, that is, in Jesus.”Acts 19:4
For we were all baptized by one Spirit so as to form one body—whether Jews or Gentiles, slave or free—and we were all given the one Spirit to drink.1 Corinthians 12:13
3. And then there is the baptism within for the work of ministry.
On hearing this, they were baptized in the name of the Lord Jesus. When Paul placed his hands on them, the Holy Spirit came on them, and they spoke in tongues and prophesied. Acts 19:5-6
Those who accepted his message were baptized, and about three thousand were added to their number that day.Acts 2:41
For further study on this question for answers I would look at the different ways that God heals, sometimes in an instant, sometimes it takes time, in conjunction with spiritual adversity, un-forgiveness, and other hindrances. However if you are believing for healing I would not be studying anything other than healing scriptures or saturating your heart and your mind with the word of God, for peace, rest and to build faith that casts out fear.