Why is this an issue?

Complex boolean expressions are hard to read and so to maintain.

Noncompliant code example

With the default threshold value of 3

If ((condition1 AndAlso condition2) OrElse (condition3 AndAlso condition4)) AndAlso condition5) Then  'Noncompliant
  ...
End If

Compliant solution

If ((MyFirstCondition() OrElse MySecondCondition()) AndAlso MyLastCondition()) Then
  ...
End If