For the Mother Superior, I had to attempt to charm her, then leave her room (going in the secret room worked), then back to her room. Only then did the hypnotise prompt appear.The most important query here is did you learn the hypnosis training from Mr Beasley? This is needed for some of these cases.
Otherwise all have criteria needed to allow the process
Gabby - you never use hypnosis on her, just the normal charm spell. You need to have spoken to some people first to overcome her defence
Mother Superior - did you possess her twice
Adele - generally it just takes time, Catherine will call you, visit and cast the charm spell
Still working on Adele. Did the first charm, but didn't have hypnotise yet when Catherine texted. Hoping it wasn't a times event that I missed out on now, and it will retrigger.