High-performance order storage (HPOS), formerly known as custom order tables (COT), is the name given to a new way in which the core WooCommerce plugin plans to store data inside the WordPress database. Please see this page for additional information.
As of version 5.5.0, WooPayments is compatible with HPOS and should function with it enabled. However, HPOS itself is still considered experimental, and should only be enabled on staging or test environments. It is not yet ready for use on production sites.