The first course saying “Sold Out”, but with no sales appears to have been accidentally switched to the Sold Out post status. I’ve re-published the event and it’s no longer sold out.
The “An error has occurred:
We’re sorry but your request failed to pass a security check.
Please click the back button on your browser and try again.” message can be the result of the elements removed from the ticket selector template. May I ask has anything been modified in your copy of the Event Espresso plugin? If not, would it be OK to update to the current version of Event Espresso 4?