I lost my ass on reta

I have been on reta for three months and i love absolutely everything about it- except i used the have the juiciest most voluptuous ass and now it’s flat as a pancake and i don’t know how to get it back. My main form of exercise is mat pilates which includes lots of glute work and yet my ass is still flat. help! if anyone has any advice on how to get some shape back, I welcome it. Thank you!