Muslim wife not staying together since 2 years, what to do

Respected Sir: On behalf of my son, I am presenting his case, for advice from a Muslim Law Lawyer. “We are Sunni Muslims, married for 4 yrs. As my wife has been working in another country, she agreed she would join me permanently after about 2 years of marriage. So, we arranged to meet as often as possible. This arrangement has been working well for about 2 years. Recently I reminded her to join me on a permanent basis, and she informed me that she did not want to join me now and gave vague reasons, without any commitment. Now, she does not call or answer my or my parents’ calls or messages etc. No communications at all from her, although I keep calling her and sending her WhatsApp messages, trying to know her welfare and well-being, either directly or through my inlaws etc. My efforts to reconcile and counsel her through her family also went futile so far. Please advise the steps to be followed in order to sort out the issue amicably, if possible.”  Kind regards.