Read Sue Witcombe's outstanding experience on the perspective of erased parents: Powerless: the lived experience of alienated parents in the UK
See Dr. Many Mathewson paper summarizing her research, entitled The Forgotten Parent: The Targeted Parent Perspective of Parental Alienation .
Joining a support group can be very helpful, and a directory can be found here. Reading everything you can about parental alienation can be quite helpful.
The erased parent has a lot of grief to process, and this article on grief might help, and this article on the stages of grief of losing a child to parental alienation.
In the words of the DSM-5 authors "The rejected parent's distress and both the parent's and child's affect, cognitions, and behavior can be affected in such instances. All types of parent-child issues that rise to the level of impact required for diagnosis are likely to have significant implications for the child's, and possibly caregiver's, mental health."
And study the ways to reconnect with your child. One of the main themes is self care, which is needed to up the odds of reconnecting.
The National Institute of Health Published a paper on the Long-Term Effects of the Death of a Child on Parents’ Adjustment in Midlife that uncannily applies to the loss of a child through parental alienation. The pdf version can be found here. Some relevant excerpts include:
"bereaved parents reported more depressive symptoms, poorer well-being, and more health problems and were more likely to have experienced a depressive episode and marital disruption than were comparison parents. Recovery from grief was associated with having a sense of life purpose and having additional children
The death of a child is one of the most painful events that an adult can experience and is linked to complicated/traumatic grief reactions (Prigerson et al., 1999). For parents, the dissolution of the attachment relationship with the child elicits severe anxiety and other negative emotions associated with loss (Bowlby, 1980). Parents might also experience guilt about having been unable to protect the child (Gilbert, 1997). Furthermore, because the death of a child defies the expected order of life events, many parents experience the event as a challenge to basic existential assumptions (Wheeler, 2001).
Thus, many parents grieve indefinitely (Klass, 1999; Rubin, 1993).
Among individuals who seek treatment for protracted grief, recent work emphasizes the task of finding meaning in the loss as key to long-term recovery (Neimeyer, 1998)."
The unnatural and unjust factors that lead to alienated children prevent or significantly delay to "finding meaning in the loss". The fact that the child is alive but unapproachable further mutates the situation towards bizarre making it a challenge to find "meaning".
Here is a good article on how self-compassion is quite helpful in surviving the criticism directed at the erased parent.
D. A. R. V. O may have been used against the erased parent (Deny, Attack, Reverse Victim and Offender) when they confronted the offender.
Consider adopting a non-blaming point of view, which will at least help you be seen in a better light.