I installed solar panels in 2020 but when I put the info in it says that it can't get me home energy credit in 2020 but it is carried over to 2021, why?

[Critter-3]

Have you finished entering in all your income yet ???    Until you have a tax liability for the credit to negate it will be carried forward.  

[Opus 17]

You don’t get the credit if you don’t owe tax. If you have not finished entering your income, such as because you have not received your W-2 yet, then you don’t owe any tax right now. When you finish updating all of your financial information, the credit will re-calculate.