iPhone 7 Update issue

I have the Iphone 7 with enough memory space available on the device. I have downloaded the latest IOS 12 Software update, but the problem is every time I tap to install it, the phone starts to verify the update and then nothing happens. There is no message prompt as to what is the issue. Hence, I am not able to update my device.

Have also done the force start as well.

Any idea what could be the issue and how to solvee the problem?

TIA

Back up your phone, then factory reset, then try the update before you install your own back up.