Yes i have a OnePlus 5, rooted, VoEnabler, and MBN eu vodafone Netherlands.
SFR/RED Carrier, but i have activated both options by the chat support.
I don't have an another SIM, but i advise to you contact Bouygues/B&Y for activate VoLTE and VoWIFI natively on your SIM/Carrier
The volte + vowifi option is activated on my line by bouygues. my sim card works with its two functions on an Xaomi.
Since your phone is a oneplus 5, and you have used the same mbn file posted on this forum, there are only two alternatives to this problem:
Either the mbn file is not fully compatible with bouygues telecom. (I have tried other files they are not either)
Or i must root the phone and activate the VoEnabler module for the volte to work properly.
How does the VoEnabler module work, and what does it do exactly?