Hola Sheveck,
Unfortunately BMA is no longer accessible from Duniter app for YunoHost from YunoHost v3.7.
The discussion have been held in French: BMA protégé derrière le SSO depuis YunoHost v3.7?
I didn’t had time to dig this issue.
If you want more details or explanation, and you don’t get the French post I can tell you more about the issue, or translating any part of it.