WHAT IS THE CAUSE?
The answer to asking what the cause of the distress may be could be as evident as something like unforgiveness, intentional disobedience or unrepented sin. (Check out Kingdom Forgiveness on the Menu.)
There is no value in trying to find out what a likely cause of the trouble is.
If a specific cause is known the Believer should go to the Throne of Grace and renounce it before the Father, repent, ask for forgiveness and thank Him.
Going through a process of trying to find a cause is at the least a distraction. But, more commonly, the distraction will be used by the enemy. If a cause is unknown, leave it that way!
The prime point is: the enemy has no legal power over any Believer.
Power may be ignorantly handed to him when a Believer has become vulnerable by being tricked into one of his "devices", or giving way to temptation.
Or perhaps he took advantage due to a Believer's ignorance of the word of Christ.
All in all, he is only able to exercise his power because a Believer gives him opportunity to enter in the first place.
The enemy's primary and most frequently used device to gain entry is to challenge the word of Christ. He did it first with Eve in Genesis 3'1.
He asked his innocent-sounding question: "Has God indeed said?". And what happened next resulted is being felt right up to this moment.
Keep the word of Christ in mind:
"... lest Satan should take advantage of us;
for we are not ignorant of his devices,"
2 Corinthians 2'11.