Had similar problems with eldest son years ago now all sorted and he is with a lovely partner and very happy. Not money problems just a dreadful woman he had a child with. Youngest son 3-4 years ago went missing for a while while abroad was frantic.
I can speak to my OH and had friends too that would listen which helped a lot.
I hope the situation resolves itself is your son maybe depressed when our youngest was and is depressed he tends to not answer texts regularly or emails he does let us know he is ok but remains very un-communicative until he feels able to cope better. I found as long as I know he is alive I let him have his time to deal with it and then he bounces back.