Activate the Formulas tab of the ribbon.
Make sure that Automatic has been selected in the Calculation Options dropdown.
IMHO, F9 shall work independently of this setting. Ctrl+Alt+Shift+F9 gives bit more, but it depends.
Hi Sergei, I am aware of that, but the OP stated "we have to keep pressing f9 function to populate changes". I took this to mean that automatic recalculation has been turned off.