Hi
I added an authenticator to my wow account this week. I know it has been a long time.
It is working, as I had to use it to log in and create this post.
As the title says, once in game, it is not detected. I cant customize posting for m+. Just a link to say I need to use an authenticator.
Any idea, suggestion, etc ?
Adding custom entries to the LFG tool requires SMS notifications to be active for the account, in addition to the presence of an authenticator. It would seem likely that this may not have been actually enabled yet - for details on the topic, please have a look here. 
Thank you for this clarifying answer.
The struggle is that only one account can be attached to SMS. The authenticator works across multiple accounts. I looked but was unable to find how to remove SMS notification from another account. In my battle net details for example, the phone number field is blank in both accounts. Guidance/links welcome