Why can't I enter tax paid b installments - clicking on the line - as in prior years - doesn't allow entry - you just get an error Bong?

To record tax paid by installments:

Under Setting Up tab choose Your Tax Profile Summary, click Edit for Other Credits & deductions.  The second last question on this page is Did you make tax installment payments for 2017.  Click the Yes button and a screen comes up with a box to enter the amount of the installment payments made for the 2017 tax year.