Please try each step until you resolve your issue:
Tap Settings > General > Date and Time > Set Automatically > Off. Set the date one year ahead. Then try to access the App Store.
It may be a connection issue. Try changing your DNS settings to Google’s open DNS by tapping Settings > Wi-Fi >, tap the blue arrow next to your current Wi-Fi network, and then tap the “DNS” field and enter the DNS servers; 22.214.171.124 (Google’s Public DNS).
Close the App Store completely by pressing the home button twice, pressing and hold the App Store icon until it starts to wiggle, then tapping the minus sign to close it. Re-launch the App Store.
Close and relaunch the App Store. Double press the home button to get to the app switcher and swipe up on the App Store. Tap on the App Store icon again. This especially works if you are using an iPhone SE
Restart your device by pressing and holding the sleep/wake button until “Slide to Power off” appears.
Launch the App Store; if it is still blank with nothing shown, wait a few minutes. Sometimes apps may load slowly because of networking issues.
If still nothing appears, try changing the device’s language by tapping Settings > General > International > Language. Pick a language. Pick any other second language you already know or be familiar with. If you don’t, do not forget to navigate back in a different language. Change the language, launch the App Store, then change the language back to what it was originally.
Sign out of your Apple ID by tapping Settings > iTunes & App Store, tap your Apple ID and select “Sign Out”. Wait one minute and sign back in by reentering your Apple ID and password.