Why can't some users load checkout on my new website?

[Horeoreo]

Hello everyone,

I've just opened a new shopify website a few weeks ago. After noticing lots of people where leaving their items at checkout I wrote an email to some of them to ask if they had any technical issues as it was suspicious. It seems that some of them are not able to load the checkout. I'm trying to run the issue but I can't – it's working on my computer. The users describes it as "checkout is not loading". I can tell the one having the problem, seems that they can add their shipping address but not go to paiement (paiement info are always missing). Does anyone have an idea? Is this a theme issue?

Update
Actually they receive a message when using paypal "no delivery available for 0 items"

https://kitsuneandjo.ch/ -> link to my shop.

Thanks for taking the time to reply !