Feeling unforgiven by someone can be very unpleasant. Your mind may go over and the situation with that person, trying to figure out over and over again how to get forgiveness or what went wrong or if it was even your fault. But none of this changes the situation.
Here are ways to change the situation:
1) Have you asked for forgiveness? This is the first and most important step. Even if you think you did nothing, have you listened to why they feel the way they do and said you were sorry for the way the situation made them feel? If so, and they haven't forgiven you,
2) Are you respectful and kind to the person when you need to deal with them? This may help the other person to understand that you perhaps did not mean to harm them.
3) Don't keep apologizing. This will make them less apt to forgive you. Once is enough. No one wants to feel coerced into forgiveness by the person they feel harmed them. Time and space may be necessary for forgiveness.
4) Some people need to hold onto resentments for some reason that you may never know. You can't do a thing with this type of person except treat them with courtesy and hope someday they come around.
5) The only person you can change is yourself, not another person. What lessons do you learn with someone refuses to forgive? How do these lessons make you a better person? If they never forgive you, but you as a result are a better person, then they have given you a great gift.
6) Let go of them, and forgive yourself.
Warmly, Cheryl Deaner, LMFT#36764