target line chart display null when select year=2020

Hi All

My chart and table behave okay when i select year=2021 

Notice that left side the line chart display 2 dot is correct because it is 2021 Jan , only 1 month data.

But when i select year=2020 , the table able display sales and target amount. But then the line chart

display Null.

Note that right side the table , it can display both sales and target amount from jan till dec 2020.

Note :- during Dec 2020 , the left hand side chart working fine , it can display 2 line one is sales another is target line.

Hope some one can share with me why ? 

Paul