we can not see your return so these are guesses. If you are seeing "Ready to mail," it means you chose the File by Mail option instead of e-File. there is no signature for an e-filed return but rather the prior year's Adjusted Gross Income is needed to e-file. Another reason could be that you need to attach a form that Turbotax does not support or you are trying to file when a form in your return is not final for 2022 but you should have seen that warning.
I recommend you contact support who you can allow to review your return to find the reason
Contact Customer Service
5am-5pm Pacific Time (8-8 Eastern) Monday - Friday
https://support.turbotax.intuit.com/contact
800-446-8848
