Why can’t I enter my 1099-R now manually. It says wait to Jan. 11th. I want to entered it manually

If you are using the Desktop installed program you can enter it in Forms mode.  Click Forms in the upper right (left for Mac).  

If you are using the 2024 TurboTax desktop editions, click on Forms.

When in Forms mode click on Open Form in the upper left of the screen.  Type in 1099-R.  Click on the result to open the form.

If you are using the 2024 TurboTax online web-based editions you will have to wait for the software to be updated on 01/11/2025.

...OR ...just use the What-IF worksheet in the 2023 desktop software (if you have it) to get an approximation of what you might want to pay for the 4th quarter estimated taxes by/before 15 Jan.

Personally, I've created a test 2024 file in my 2023 desktop software, entering data as-if received during 2023....thus able to get in all my late December Mutual Fund distributions, that can be all over the place.  That will likely overestimate my 2024 taxes a bit, but it will let me get pretty close and let me know if a 4th Qtr estimated payment is necessary.  (I usually overpay the first 3 quarters, on purpose)