In almost all situations, there are better ways to communicate than with an apology. Your persona should show empathy and emotional intelligence by offering solutions, not apologies or excuses. Furthermore, your persona should take responsibility, never blame the user, and never blame another party. People think less of individuals who blame others for failure.
It’s okay to use “sorry” when it serves a transitional social or phatic function and is not a full-fledged, heartfelt apology. If you can remove “sorry” without changing the meaning, then the function is transitional. For example, the reprompts “Sorry, for how many people?” and “For how many people?” convey the same meaning.
“Sorry” is most helpful in no match prompts to make it clear to the user that your persona couldn't understand or interpret their response in context. But avoid overuse. For system errors, avoid saying “sorry” when it’s not your persona’s fault.