Short answer
Counselling may be considered when communication repeatedly fails, disagreements become persistent, emotional distance continues or the couple cannot identify a workable solution themselves.
Islamic Guidance
What Islam teaches
Islam encourages reconciliation and permits seeking assistance in resolving serious marital disputes. The aim should be fairness, reconciliation and protection from harm.
Practical Guidance
What you can consider
Consider a qualified and trustworthy counsellor who respects the couple's privacy and cultural and religious context. Medical evaluation may also be appropriate when health concerns are involved.
Sources
Qur'an 4:35.