maybe try some different methods of communication, for example:
- automatic writing
- asking for messages in dreams
also, if you are performing results magic… you don’t necessarily need to evoke the spirit to any kind of presence in order to get results. you can instead petition them/task them with something, which doesn’t rely on needing a two-way communication method.
if you’re doing it for practice or because you are developing that two-way method, then the best thing to do is just keep practicing.
you could also consider creating a sigil, a servitor, or calling on another entity, for assistance in kickstarting your subtle senses (clair-senses).
also (I say this without knowing your background/experience/etc.) consider what your expectations are. the smallest, most subtle change can signal a presence, something that could easily be overlooked: a change in room temperature, a slight breeze, ringing in one ear, seeing shadows or flashes of light from the corner of your eye, a candle flame changing rhythm and form, goosebumps, persistent muscle twitches. unless you’re in a heavily altered state it’s unlikely that you will see Raphael physically standing before you, or hear a discarnate voice.
edited again to add: there is no set measure of time, unfortunately, but practising is the best thing you can do, as well as taking any signals of a presence, no matter how small or coincidental it may seem, as a sign of encouragement.