Sorry, I don't know know why it's not letting you change it. If you don't get any other suggestions in this forum, here's how to phone TurboTax Support during business hours.
Please report back in this thread how they had you solve it, and it might help someone else.
Hours are 5AM-9PM Pacific (8AM-12 Midnight Eastern) 7 days.
You can use this contact form to get an incident number and phone number.
https://support.turbotax.intuit.com/contact
