In fact it's just 1 device that has the issue.
Tried on other GS6, GS7, simple, plus and/or edges for both.
Even on other applications (even the Oculus home), I can't have access to that menu, but the system is up to date, so that's very strange..
It worked today O.o
I haven't added it in every scene but my gameObject has been "DontDestroyOnLoad", so it's the same.
I don't understand..
Before I had a kind of black screen with an Android log that told me that the UM wasn't installed....