Hey Howdy Hey Nicole and welcome to planDisney!
Thank you so much for your question about linking tickets, I know I have had my share of struggles with this as well so I wanted to share some options that hopefully will work for you.
The first thing you are going to want to do is to log onto your
My Disney Experience account online as many times for me the app would not work but the website did, go figure! You should see a Walt Disney World external ID/confirmation number from Costco confirmation communications that would be the one that you will use to link to the site. Now, as you have tried before, go to the Tickets icon and "Link Tickets" button and try it again. Hopefully, that helps but if all else fails you can
call Disney and a Cast Member will be happy to help you through this process.
One big thing to note with buying tickets other than the Walt Disney World site is that you need to make your
Theme Park Reservations as well as have your tickets. This part is no extra charge, just more of a planning thing for Disney. So after you link your tickets you can use the
Theme Park Reservation Availability tool to help you plan which parks on which days you want to visit. Then make sure you make your park reservations as well.
I hope this helps and works smoothly to add your tickets and continue the planning. If you have any further questions please let us know, we love talking about all things Disney!
Happy planning,
Nick