Box 12 Code

I suspect that you will have to wait for TurboTax to be updated. On January 8, 2024 (i.e., just two weeks ago) the IRS released a notice describing many changes required to implement the Secure Act 2.0 - I believe that this is what "We're updating how SEP and simple plan contributions are reported on the tax return based on new guidance from the IRS." is referring to.

Indeed, Section 601 of the Secure Act 2.0 refers specifically to Simple and SEP Roth IRAs. Code S in box 12 refers to how to handle a SIMPLE plan.

These last minute IRS (and law) changes inescapably cause delays on the part of TurboTax and other tax processors. 

It will take time for TurboTax to understand all the ramifications of this IRS Notice and then code and test the changes. The IRS is not open for filing until January 29th so you have some time to wait.

Any word of an update?

It's now past the 29th and it's still not fixed.

Thank you!

They're working on it.  See this recent employee answer for W2 box 12 Code S
https://ttlc.intuit.com/community/after-you-file/discussion/it-wont-accept-the-letter-code-s-in-box-12-of-w2-how-can-i-get-passes-this/00/3155763

Did you get it to work?

Try leaving the cents off in box 12.   That has been working for most people.