Sennies are notoriously one person birds. If he just lost his beloved person thru death, he is mourning and angry (not that the bird understands death, only that his person who he may have loved and been bonded to is suddenly gone). Then he is sent to a store with other birds and not sure what happened there... then you come along to give him a new loving home, but for him, all he knows is that you're not his person.
Adult sennies will pick their person. We have adopted quite a few sennies at the shelter and actually I live with a male Senegal from the shelter (Mali was about 25 when my husband met him). Mali had been at the shelter for some time, he was generally friendly, but when he met my husband, it was clear he very much adored my husband. Love my hubby but he's a guy who enjoys the fun stuff but doesn't like cleaning cages and such, so he just enjoyed visiting Mali at the shelter, but never asked about adopting him. So for almost a year, we continued to introduce Mali to potential adopters and everytime after meeting Byron, Mali end each meeting with a potential new home with the adopter bleeding. After a year of this, the decision was made that I had to suck it up and accept I had another bird cage to clean

And while Mali loves my husband does pretty well with my brother, he hates me and I do mean hates me. He'll let me scratch his head when he's in the mood for a head massage, but if I ask him to step up, there will be bloodshed. He'll step up on a towel and I put him on a java stand to hang out, but going back to the cage, he does his best to get past the towel and to flesh.
He came home Valentine's 2015 and I have tried every training suggestion from every professional, every trick and bribery, but it simply comes down to the fact, the bird does not like me. End of discussion...
So, the point of my babble... one, you need to give this poor guy time to realize that his life has changed. Second, you may need to accept that you are not the guys chosen person. Doesn't mean you can't come to a mutual agreement, maybe do stick training for taking him in / out of the cage. Head scratches on his terms, accepting treats, things like that. But you may never have that hands on relationship.
For now, give him time. Its a huge change for him and no way to know his path between losing his person and ending up in your home, exactly what happened.
Thank you for giving the guy a chance at a new life and I hope it turns around for you, or at least you can find a way to enjoy a peace treaty with him!!