Hi there Markus,
Welcome to planDisney and thank you for your question. I'm sorry to hear it's under these circumstances, but I hope I can help give you some information and suggestions for a next step.
I'll start by saying that
standard theme park tickets purchased through the Disneyland Resort website state in the
eTicket Terms & Conditions that "Multi-day tickets purchased through Disneyland.com or the Disneyland app today must be used within 13 days of first use or by January 12, 2026, whichever occurs first."
If a third-party seller stated different terms & conditions for the tickets you purchased through them then I would first recommend reaching out to them to get some more clarity on your original understanding of what they told you.
If you don't end up having any options with them - Hakuna Matata! Most standard theme park tickets that expire are able to have the remaining value of those tickets applied toward the future purchase of tickets as long as the new tickets are of equal of greater value.
Therefore, the next step I would recommend would be to
call a Cast Member at the Tickets line so they can get more specific details of your situation and let you know what options you might have. I've had to do this a few times over the years and I can personally vouch that the Cast Members who do this are incredibly helpful!
Thank you again for your question, Markus! Sorry again to hear about your frustration but I hope this helps you figure out a solution that you're happy with.
Have a Magical Day,
Greg