Hey there Gabriella,
Welcome to planDisney and thank you so much for your question! I'm sorry to hear your plans changed and hope you're feeling better now!
When I'm planning my trips and trying to coordinate dates, I like to use the
Theme Park Reservation Availability Calendar. When looking at the 1 Park Per Day Ticket tab, I'm still seeing quite a bit of reservations available over the next few weeks - including on February 18, which is the arrival date it looks like you indicated on your question.
If you're having trouble updating your reservation, the first thing I would try is visiting the
My Plans page to see if you can make them through the Theme Park Reservation link on that page.
I have noticed that if a theme park reservation is not modified or canceled before the reservation date, it can sometimes require
calling a Cast Member at the Guest Information line to help reset your theme park reservation in the system so you can make a new one.
Either way, calling a Cast Member would be my recommended next step if you're not able to update that theme park reservation on the My Plans hub. They should be able to look into the details of your specific situation and let you know what next steps will be needed.
Thanks again for reaching out Gabriella! I hope you are fully recovered and have a fantastic visit to the Disneyland Resort.
Have a Magical Day,
Greg