Most professing Christians have no fellowship with God because they do not know Jesus Christ and they do not have fellowship with Him.
The Apostle John explained this in 1John 5:20 (I read from the New Living Translation) “And we know that the Son of God has come and He has given us understanding, so that we can know the true God, and now we live in fellowship with the true God, because we live in fellowship with His Son Jesus Christ. He is the only true God and He is eternal life.” If you do not have Jesus Christ you do not have life.
The Apostle John writes here that Jesus came and He gave them, the disciples, understanding, and that same understanding that He gave to them, He also gives to us, that He Himself is God, and that if we live in fellowship with Jesus Christ then we live in fellowship with God. But if we do not have Jesus Christ, if we are not in Christ, and Christ is not in us, then we do not have fellowship with God.
Most professing Christians just believe in Jesus Christ for salvation but they do not know Him, and therefore they will perish. They do not know who Jesus is. They do not know that Jesus is God. As we have just read here:” and now we live in fellowship with the true God because we live in fellowship with His Son Jesus Christ. He is the only true God, and He is eternal life.” Jesus Christ is the WAY and the TRUTH and the LIFE.
Do you just believe in Him or do you know Him? Because if you do not know Jesus Christ, then you do not know God, and you are lost. Has Jesus given you understanding?
Go on your knees before Him. Seek Him with all your heart, and you will find Him, and He will give you understanding, and you will know that Jesus Christ is the one and only to God. Without Jesus we can do nothing.
May Jesus bless you.