I bought 1 tickets for Bailuyuan Ski Resort on the road travel website, but I missed the skiing date because of something. Are these tickets invalid? Can I return it?

Generally, ski tickets are within the validity period. You can choose the weekend and week according to the ticket type, and they should not be invalidated as long as they are not used after the day. Invoices are usually issued at the time of payment. Specifically, you have to ask their customer service. 17tutu has it on their website. If you really don't need it, it's probably not convenient to return a stressful project like this, and you can transfer it to someone else.