Under which condition can no auction price be determined?

The situation where no auction price can be determined typically occurs when there is an imbalance or lack of sufficient orders in the order book to establish a price. In this context, when only market orders are present on both sides of the order book, there is no designated price at which these orders can transact.

Market orders are designed to be executed immediately at the best available price. If both sides, the buy and sell, consist solely of market orders without any limit orders to anchor the potential auction price, the system has no reference point to establish a specific auction price. This leads to a scenario where transactions cannot be executed at a defined price level, resulting in the inability to determine an auction price.

In contrast, other conditions mentioned, such as having a potential auction price outside the market order matching range or being in a fast market period, do not inherently block the establishment of an auction price but rather may influence its execution or feasibility. Additionally, the triggering of stop orders relates to the execution of those orders rather than the establishment of an auction price itself.