Is online / proxy Pind Daan valid according to Hindu scriptures?

Yes. The Dharmashastra texts explicitly provide for proxy performance of rituals when the principal performer (karta) is unable to be present in person — due to illness, distance, or other unavoidable circumstances. The condition is that the proxy (our pandit) acts with the full authority granted by the karta, the Sankalpa names the karta and their ancestors correctly, and the karta participates in intent and prayerfully. Our live video call format satisfies these requirements. Many respected scholars and the Shankaracharya tradition confirm the validity of properly performed proxy rituals.