In the beginning, in the Garden of Eden, there was no sin and no sickness. After the fall, sickness and death happened. Micah 6 affirmed this positive correlation:
Jesus spoke to some scribes in Mark 2:
Jesus healed the paralytic by forgiving his sins.
On the other hand, Jesus stated a non-correlation in John 9:
Let proposition S1 = if a person sins, he will get sick.
S1 is false, i.e., S1 is not universally true for everyone without exceptions.
Generally speaking, there is a positive correlation between sin and sickness. In specific cases, however, the correlation could be 0.
We are also subject to OTHER'S sins as well, through no fault of our own.
Jesus did say many times after healing someone say "go, and sin no more".
Here is a short article that points out several reasons, from Is Satan always the cause of sickness? - Christian Research Institute
By Hank Hanegraaff
"If you tune in to Christian television on virtually any given day, you can hear faith healers screaming at satanic spirits of sicknesses' ranging from asthma to arthritis. But is Satan really behind every sickness?
First, while Scripture makes it clear that Satan is often the
agent of sickness, he is not always the
author of sickness. Sometimes God is. For example, in Exodus 4:11, God Himself asks the rhetorical question “Who gave man his mouth? Who makes him deaf or dumb? Who gives him sight or makes him blind? Is it not I, the Lord?” In 2 Kings 15:5, we read of the Lord striking King Azariah with a skin disease from which he suffered till the day he died. And in Luke, the angel of the Lord came directly from God’s presence to strike Zechariah with an affliction because he doubted God’s word regarding the birth of John the Baptist (Luke 1:19–20).
Furthermore, we live in a cursed creation in which aging is the primary sickness of humanity. Thus, humanity’s fall into a life of constant sin terminated by death, rather than Satan, is by far the primary cause of sickness. As we get older, we all get wrinkles, some of us need glasses, our muscles get shorter, and eventually we all die. Since the fall of humankind, both the righteous and the unrighteous have been subject to sickness and disease. Job, who is affirmed in Scripture as a great man of faith, was covered with painful sores from the soles of his feet to the top of his head (Job 2:7). Paul confessed to the Galatians that he preached the gospel to them for the first time because of a “bodily illness” (Galatians 4:13 nasb). Timothy was called Paul’s “son in the faith” (1 Timothy 1:2), yet he suffered from frequent stomach problems (1 Timothy 5:23). And Elisha was blessed with a “double-portion anointing,” yet he suffered and died a sick man (2 Kings 2:9–12; 13:14).
Finally, it is crucial to note that this world is under the sovereign control of God, not Satan. Thus, we can rest assured that even in sickness and suffering, all things work together for good to those who love God and are called according to His purpose (Romans 8:28). For the child of God, the hope is not perfect health in this lifetime but a resurrected body in the life to come. As John the apostle so beautifully put it, “‘There will be no more death or mourning or crying or pain, for the old order of things has passed away.’ He who was seated on the throne said, ‘I am making everything new!’” (Revelation 21:4–5)."
