Greetings and thanks for posting on the forums.
First, even thought i have 'show quantity' checked, it doesn't show up on item listing page.
The quantity is only displayed on single product page and not on listing page.
To display quantity on the listing page use solution provided on the following reply.
Secondly, the quantity does show up in the 'view cart' page, but if you change the number and then click 'update cart' it just goes back to 1.
I have tested it on my test site and it's working fine.
You have not added products / tickets in your store therefore the provided product page link is not working and displaying Page Not Found error.
Could you please add some products / tickets in your store so that i can test the update quantity in the cart issue on your site?