Puppy Anxiety? Looking for advice

Good people of the Redit world. I am here for advice. My pup is 9 months old. He just came back from a 7 week board and train program. He did great with the training. And I was very hopeful it would help with his separation anxiety. However. He is very much a Velcro dog. He whines, cries and barks if he is away from me even if he can see me. If I am to leave him with someone to go run an errand, same behavior. I was thinking Maybe it’s because he was away and now is back, but that behavior was happening before he went to training. I am wondering, have any of you dealt with this? What did you do to correct it?thank you as always!