None of my Maxis have been total perch potatoes. They all have active and nappy times and when active they either fly or run and walk everywhere. I think you just have to find the magic toy or treat that gets him excited. All my guys loved bells and things to beat up.
Maybe a foraging toy with high value treats will do it. Lurch didn't even come out of his cage except once for the first 6 months he was here and was scared to death but as he slowly realized I was safe and he got comfortable he slowly came out and got closer and closer to me.
Dobby was completely different and was out and getting into things and interacting immediately because of his loving upbringing and always good interactions with the family he loved, it carried over when he came here, completely different attitude. They truly are all individuals with similarities and individual traits.