Hi Ly,
Thanks for getting in touch, and sorry to hear about this issues you are having. I’ll help you getting this right!
If you are saying the paid tickets are not showing up, I guess maybe Event Tickets Plus or the e-commerce plugin (WooCommerce, Easy Digital Downloads, WP-Ecommerce or Shopp) is deactivated. Can you please check that out?
If the plugins are active and the event has not passed, please check the tickets start sale and end sale dates. If that’s correct, then please send over the event URL were I can see this.
Finally, I see you marked that this has been tested with WordPress default theme and no other plugins active. Can you confirm this? Did you notice any difference?
Best,
Nico