CHECKOUT201: Checkout outcome unknown
What this means
WCPOS could not confirm whether checkout completed.
Do not retry blindly. Check the store for the order first, then export diagnostics if its outcome is still unclear.
Your data
The outcome could not be confirmed — verify before retrying. If this persists, export diagnostics and contact WCPOS support.
Troubleshoot
First, don't make it worse: do not retry checkout and do not charge the customer again until you know whether the order exists.
Check whether the order exists — how depends on what you can reach: on WCPOS Pro, sync the POS and look in the till's Orders list; otherwise have someone open WooCommerce → Orders in WP Admin and search by the total and the last few minutes. If the order is there, the sale went through — do not create it again.
Then: if no order exists after checking, retry checkout once. If it is still unclear, export debug info and contact support before another attempt.