Dealing with adult son with mental health: Parents want to share?

My 39 y. o. son suffered 2 major losses since April 2022 & has never been the same since. He is under the care of a psychiatrist & taking trintellix & adderall which are not helping. Gradually he became more & more isolated and suspicious of all - including his parents. His therapist for 2 years recently started a new position so he has none. And not interested in getting another. I believe he checks off almost every symptom of Paranoid Personality Disorder. I live in the east, he's in the midwest, not married, living alone. I must walk on egg shells with him, an innocent remark becomes an argument. He is never wrong, but everyone else is. Recently we had a blow up over the phone, he didn't like the way I asked him a question, saying I was "abusive"...he now refuses to have any contact with me. He is my only child, our entire lives we have always been so close. His Dad & I are divorced for 17 years. His relationship with him, worse than mine. Hasn't seen him in 1 yr. I am so depressed & heart-broken. I have reached out kindly to him since the blow up & no response. I can't talk to his psychiatrist due to HIPPA laws but thought I could...but he can not talk to me about him. His mental health clinic will not allow it. He did a complete 360 with his life, unrecognizable to everyone who knew & loves him. He is very paranoid. I don't know what to do - how to help him and the longer he doesn't contact me the worse it will be.
This is impacting my entire life...I am 69 y.o. and so very sad my beautiful son has now developed this truly awful personality disorder.
Any thoughts from other Moms going thru this, greatly appreciated.