Here's the number one reason why I believe most Pentecostals are not saved.
Pentecostals in general reject the doctrine of eternal security,
which teaches that once you're saved, you're always saved.
Pentecostals on the other hand believe you can lose your salvation
based upon the sins that you commit or the works that you don't do.
However, the very essence of eternal life is the fact that it is a gift
freely given to us by God's grace,
rather than a wage that we earn based upon the works that we do.
The Bible literally says,
For the wages of sin is death,
but the gift of God is eternal life through Jesus Christ our Lord.
The very fundamental teaching of salvation
is the fact that God is promising us a life that will never end.
And so if you believe you can lose your salvation,
you're essentially saying that it can, and thereby calling God a liar.
1 John 5 verse 10 says,
He that believeth on the Son of God hath the witness in himself.
He that believeth not God hath made him a liar,
because he believeth not the record that God gave of his Son.
And this is the record that God hath given to us eternal life,
and this life is in his Son.
Believing on Jesus Christ requires for you to believe
that you can never lose your salvation.