Q: How do you update you app store it wont let me download apps

Can you describe issues in more details?

Have you tried to update your payment details?

Why can’t I select None when I edit my Apple ID payment information? - Apple Support

Turn your device off and back on. If this doesn't help, sign out from your account and sign back in.

Also, you can try resetting your settings.

• Press and hold the Sleep/Wake button
• Press and hold on the Home button
• Keep holding both buttons until the display turns off and back on with Apple logo on it.

Alternatively, you may go to Settings - General - Reset - Reset All Settings

https://support.apple.com/en-us/HT201559\

What exact error message do you see?

If you have an account and there are outstanding unpaid purchases ... You cannot download FREE Apple apps,

I'm wondering if this is behind your question.