Although you're using TurboTax Online, when testing your situation in TurboTax Desktop and reviewing the forms, the pension deduction of $43,000 was correction calculated on Forms MO-A and MO-1040.
How did you determine that it was not without reviewing the forms? You may want to close the program, clear your Cache and Cookies and review that section of your Missouri return.
Here's more info on Missouri Pension Deduction.