Our child has married an atheist. What can we do?

In this episode Dr. Betters answers the question, "Raised in a caring, Christian home with one serious issue after another in the church, our grown child has married an atheist. Our hearts are broken, and communication has now ceased. Our new atheist in-law is the only one who appears to be happy, while the rest of us seem frozen in time, and in shock. We were told we are not welcome in their home because of Who we represent, and haven't seen our adult child since the wedding, (which we almost skipped due to overwhelming issues). The wedding day was an utterly heart-breaking day and perhaps the saddest day of our lives thus far...In spite of the offerings of the normal Biblical Conflict Resolution Steps as an effort to move forward with resolving issues, this method is fully and vehemently rejected by our formerly-Christian, now married, adult child. The new in-law feels all is well. We fear the devil has his foothold on their marriage, and our family is being destroyed before our very eyes. The last thing we want is to lose a dear family member to the wilderness of a non-believing marriage or worse.. We have no assistance to mediate, and no teams of believers to surround our family in vital support. Considerations, please."