Hi philly00,
Sorry for the issues with the Add to Cart not showing. I can help you out with this.
I took a look at your site and visited the Event and saw the Add to Cart Button and was able to get to the Proceed with Checkout page with the tickets in the cart.
Were you able to make some changes to get it working? Can you please test again and let me know if there is an issue. Please try to view the site in a browser you do not normally login WordPress with or clear your browsers cache.
Let me know if you still need help and I will be happy to provide it.
Thanks