Two thoughts:
1. If your boarding passes show your AS number on them, then scan them and send them attached to an email requesting missing mileage credit to
[email protected], Ime this process takes 2 - 3 months, but the AS mileage does eventually get posted.

2. At the beginning of the pandemic, I had a LA flight where the boarding pass did not show my AS frequent flyer number, and I contacted LATAM via their US website (https://www.latamairlines.com/us/en/...er/create-case), and they wrote a "to whom it may concern" letter that I forwarded to AS at the mileage plan email address above.

Hope that this helps!