When Twin flames meet in this lifetime, they show each other how unconditional love is, if one (or both) of them did not feel this unconditional love previous in life, it is quite possible that this person is going to reject its twin flame love and run.
At that point, the person who ran is learning to feel and receive unconditional love from god, source and ultimately, from a twin flame without being triggered.
If, the unconditional love that our parents were supposed to give to us was not available, or was confusing, unsafe, conditional, then, it is very likely that our body created negative association with something that should be a positive experience, so, it becomes our blueprint. Then, we keep attracting people who are demonstrating the same kind of conditional love, this is what we know, this is what is normal for us, and what we expect, then, when someone (our twin) arrives without any warning and offer us unconditional love our body is not used to it, so, it will sabotage it (here is when a twin flame "runs").
This is our uncomfortable comfort zone, if your twin flame is ignoring you, have compassion, I bet it is in pain, and remember, that you both are timeless, so, no rush for union.