No actor can give an identical performance twice. It will only have freshness or tuthfulness if each time the performance is given it is as if for the first time. So maybe the first thing is not to stress your actor by making him/her feel that they have to replicate a performance exactly.
If the actor is not "in the moment" at all, then there are all sorts of strategies you can use to get them there. I wouldn't lecture them about feelings - nobody can produce feelings at will, not you and not even actors - they're a consequence of actions and experiences. So perhaps you could give them some kind objective to aim for. Say you want your actor to "be angry" at another character, you might ask them to "punish" or "attack" the other actor. If you start talking about feelings, your poor actor is going to have to step back and work out why he needs to be angry and what he needs to do about it and already you're distracting them from the work.
Good luck.