Just received TripAdvisor's new terms and conditions. They have nothing in them about cancellations due to Covid-19 and clause 4.5 just says
once You accept a Booking, You are under an obligation to fulfill it. If You breach this obligation and cancel a Booking, then We may impose the Cancellation Fee.
They also have this section:
We will act as Your limited payment collection agent in receiving the Traveler’s payment, however, We are not a party to Your transactions with Travelers and are not responsible for ensuring that Travelers make payments to You via the Payment Platform. As your limited payment collection agent, You understand that Our obligation to arrangement payment to You is subject to and conditional upon successful receipt of the associated payments from Travelers. We do not guarantee payments to You for amounts that have not been successfully received by Us on Your behalf from Travelers.
Given that TA handle the entire transaction, they are the ones who know whether payments have been received successfully from travellers or not.