Please deactivate all the plugins not related to the theme and switch the parent theme, check the issue, if the problem remains, leave the plugins not activated for us to check.
It’s Because One Of The Plugin Named : woocommerce Checkout manager.
I’ve Disabled the Plugin and problem has been solved.
I have to add custom text in the Checkout Like :- (Delivery will be estimated within (8-9 days) After Order. You will receive the courier tracking code before 4 days (In My Account Page)