First, please confirm the period dates (start and end) that you are trying to submit, and any error code that may show on screen when submitting.
Please note, QuickBooks cannot prepare annual accounts dated on or before April 1, 2023, or accounts that are over 365 days old. If you need to file a return that falls before this date, you'll need to consider other options.
Thank you for the prompt response on the thread, @marilena1. Let me share more information about filling your CT600.
From your previous message, I understand you are filing between December 1, 2022, and November 30, 2023. As the period is over 365 days old, I recommend filing this CT600 outside the program.
If ever you need to file for the latest period of CT600, I am happy to share this article on how to file your tax return and how to export tax info of your clients: