I entered info for my new A/C unit and I can see the credit for $600 on form 5695. However, at the end of my return, that $600 is missing in the total. Why is that?

The credit is 30% of the total costs up to a maximum of $600.

However, The credit is nonrefundable, so the credit amount you receive can't exceed the amount you owe in tax. 

IRS.gov

The answer that was provided for my question did NOT solve the issue. That answer is in the basic explanation of the HOME Energy credits section. 

I called a tech and discussed with him. The line on Home Energy Credit still showed only the Carry forward from last year but did not add the $600 I am talking about. While it was being discussed and he was researching, I just happened to add the total on that page of 'Deductions & Credits section'. 

There is a Turbo Tax software bug on the credit section. The total at the end in the bottom is correct (including the $600). However, when you add the items the total is actually $600 short. ???

So at the end the details page looks incorrect, but the calculation for tax was correctly done. So I moved forward. 

Thanks