If someone is trying to purchase tickets but is getting the error message of "The capture context could not be found. Please request another before trying again" that is due to the buyer taking too long to checkout after entering their credit card information (Number, Expiration Date & Security Code). If your event has a lot of registration questions or if the buyer has left their computer during the checkout process this can happen.
To fix this, the page should be refreshed and then all of the registration questions should be filled out first. Then enter the credit card information last. This will allow the buyer to check out.