Where are you trying to enter your date of birth?
If you are not getting an error that the date of birth is wrong and it just won't allow you to enter it into the system, I would suggest logging out of TurboTax, clear your cache, and delete cookies. Then log back into TurboTax and try to enter them again. You can also try and different web browser.
If that does not work and the issue still persists, I would suggest reaching out to Contact Support.