If your tickets are not showing up in the web or in the apps, it could be due to one of the following reasons:
Ticket Sales are not Enabled
Did you select "Enable Ticket Sales" in the auction settings? This flag will allow you to show and hide your "Buy Tickets" option easily; However you must turn it on to start.
Your Ticket Sale Dates are off
Are your ticket "Sale Start" and "Sell Until" dates valid? The only tickets that will show up are those that fall between the Sales Start and Sell Until dates listed. If the Sell Until date is in the past, the tickets will no longer appear. If the Sales start date is in the future, the tickets will not yet appear.
Your Ticket is Hidden
Make sure that any particular ticket is not HIDDEN. That is an option on the Ticket Item detail page under the "Info Tab". Look for a checkbox that says "Hide Item" and make sure that is NOT checked if you want the ticket to appear online.