Good evening Mansoor and welcome to the Events Calendar Support forum!
Thank you for reaching out to us. We are sorry to hear about the fact that the tickets are not displaying like they should.
We will gladly try to assist you on this topic.
At first glance, the main problem I see is that the client is still using the WooCommerce tickets plugin as opposed to the Events Tickets Plus plugin.
The WooCommerce tickets plugin is no longer supported and will most likely break with the latest version of WooCommerce and the Events Calendar plugins.
As a first step, after making a complete backup of everything (database and plugins), I would recommend following the instructions found here.
Let me know how that goes.
Have a great day!
Geoff B.