The only power indicator is also the hard drive activity and battery LED on the front edge of the system -- there is no indicator on the power button itself (is it the front left one that's not working, or are you expecting there to be an LED on the button itself?).

Most newer Inspirons don't have an LED num lock indicator - - it's on the screen (in the system tray only).

Thank you ejn63 for your kind reply.

I was talking about the indicator light in the power button itself as most system have the same. If there is no LED indicator then my question was wrong. One more thing, the num lock indicator is also not appearing in system tray also. How can I fix that? Your reply will highly be appreciated.

There is no LED on the power button itself.  As for the num lock indicator, is this the factory installed OS, or did you or someone else install Windows onto it yourself?

The factory installed system was windows 10 home, but later on I upgraded it to windows 10 pro. Is it the reason behind non indication of num lock in system tray? If so, then what can be the fix for it. Thanking you in advance.

If you did an in-place upgrade (just using the product key), the drivers should have remained.  If you did a clean install, make sure you installed the necessary chipset drivers and then the Dell quickset application (under Applications, here):

www.dell.com/.../advanced

I did in-place upgrade, so drivers should be there. I also followed steps suggested by you i.e. installed chipset drivers and dell quickset application. But, problem is still existed there and num lock indication not coming in system tray.

Thanking you.