I am having the same issue with 11D. BUT, it does not happen all of the time.
Sometimes, especially after a cold boot, BE will mount a tape as it is inserted. When it is working like that I can eject and insert tapes and it will continue to mount them.
Then, after a couple of days it stops mounting automatically.
Furthermore, before we upgraded to 11D, (v10) it ALWAYS mounted the tape automatically upon insertion.
Has something in 11D changed? And, what would make it intermittent?