I would like to change message
"Sorry, no quotes are available for this order at this time"
In which file, i can change? Can it will be manageable by Admin?
You can change this message from CSV file.
Below is the location and name of csv file
vendor/magento/module-checkout/i18n - en_US.csv
Override it in your custom module or theme and replace your message with default.
Also it is not manageable from Admin.
magento\app\design\frontend\Custom\ThemeName\Magento_Checkout\i18n\en_US.csv
& i changed second value still it's not working
You can use csv(translation) file to change it as it can not be managed from admin
There is a simpler way of changing that text.
Copy this file: vendor/magento/module-checkout/view/frontend/web/template/shipping.html
to your custom theme at this path: app/design/frontend/YOUR-VENDOR-NAME/YOUR-THEME-NAME/Magento_Checkout/web/template/shipping.html
Change the text in line 82, which will begin with: translate=" 'Sorry....
You can change the text between the single quotation marks to whatever you would like to display on the frontend.