Buybox?? What happened to it?

We were having good sales prior to prime day. Suddenly our buyboxes went from30% to 3% and now 0. What is going on? All the matrices are good. Our account health is in good condition. Odr is below 1%. Connecting with Amazon solved nothing. Their agents say our is algorithmic. What have we done wrong? Is there any one else facing the same issue or we are alone? How did you solve it?