Rebuilding trust is a pile of small deposits, not one big speech.

Trust is built out of records rather than statements. One long apology, however sincere, changes little by itself, because what got damaged was a prediction about your behavior and only behavior updates that. Small, boring, repeated evidence is the entire mechanism: turning up when you said you would, answering when it is inconvenient, doing the thing without being chased.

If you are repairing something, stop explaining and start being predictable. Choose three small commitments and keep all three for a month. Let the other person take whatever time they need to believe it.