ホームページ上で予約の確認ができませんって英語でなんて言うの？

Sometimes when you book a room, the email that you receive in reply will have a link. The link might say something like "View your reservation". If you click on it, you should see the information about your reservation, plus it may have some other useful information like check-in times (often 3pm in the US). But sometimes nothing will happen or you may get a page that says "404 page not found" (why 404? sorry, don't know). That's an example of a broken link.

example "confirmation", or Booking Conservation", or "confirmation of booking". "hi I can't find my booking confirmation?" or "I have not received a confirmation of my reservation yet". or "Can you please resend my booking confirmation".

Explanation: If something you believe exists but you cannot find it when looking on the correct page, you can say that this piece of information 'is not showing.' Example sentence: "The latest financial figures are not showing yet as the New York stock exchange is still closed for the night."

Booking, book, booked - is the act of reserving accommodation, a ticket, etc. in advance of your arrival. 'Appear' and 'show up' mean that something is visible and can be seen. So to say that they have 'not' appeared or shown up, is to explain that you cannot see them.

"I can't find my booking on the website." This explains to the person that you can not find your booking on their website. "I can't see my booking on the website." This is another way of explaining that you can not find your booking on their website.

When you book a hotel room it is either called a 'booking' or a 'reservation' so if you can't find it then you would say 'I can't find my booking/reservation' by adding 'on the website' you are explaining where you can't find it

This is an uncommon technical error and you would need to be specific for the other person to understand. The information they need is first the problem (You can't find your booking) and then the location of the problem (The website)