"You're welcome, Maha."
Translation:عَفْواً يا مَها.
The way I was taught, the nunation diacritic goes on the letter before the final alif, not on the alif itself. So عفوًا.
And for those wondering, in Arabic, the final -un and -in, which express the nominative and genitive cases, respectively, are only written as diacritics, but -an, the accusative marker, actually changes the spelling of the word by adding a final alif. That is because, at the end of an utterance, you wouldn't pronounce the -un or -in at all, but would replace the -an with a long -aa sound. At least in Standard Arabic. The set expressions like shukran and 3afwan are always pronounced with a final -an in the vernaculars, even at the end of an utterance. Nobody would ever say "shukraa" in day-to-day speech.
There is a Palestinian woman who teaches Arabic on YouTube whose name is Maha (Learn Arabic With Maha). She pronounces her name "mah-hah using the European "a" sound "ah" rather than the English "a" sound like the "a" in "hat" that Duolingo is using. Are both pronunciations used or is Duolingo's TTS pronunciation incorrect again? I'm assuming Maha knows how to pronounce her own name correctly. ; )