"Vasas are enthusiastic bathers, and they need frequent bathing opportunities. They also enjoy sunbathing and dirt bathing, which is uncommon for parrots. An aviary or flight cage setup is ideal for vasa parrots because it offers more ample space for these very active birds to fly and room to explore. Vasas are good eaters and appreciate a variety of foods, such as fresh fruits and vegetables along with a pelleted base diet." Quoted from Greater Vassa page.
So you could try offering sand in a ceramic plant thing you put under pots as dirt bath? Maybe a shallow casserole dish with a small amount of water and some floating toys to play with... Read Sailboat sticky in the Amazon forum, he has amazing advice on "Shut Down Parrots" which is what has happened to your guy, and lots of info on rescued Parrots! Even though he talks about Amazon Parrots I find the info very valuable and I'm useing it with my rescue parrot Penny. She was shut down lump abd I didn't even know that term but that's what she was, abd I'm still working on getting her engaged. I found some frilly paper preen toys that she has taken to! I think you could find lots of gems in his thread too! I'm reading it all carefully, and has touched my heart! Thank you Sailboat!!!!! Xoxo