Face ID not working in App Store

Hello Yombi_,

Welcome to Apple Support Communities!

We want to help you make purchases in the App Store by using Face ID instead of having to type in your password.

You should only have to do this the first time. Make sure you're taking the steps detailed here:

"Use Face ID in the iTunes Store, App Store, and Book Store in Apple Books

To use Face ID to purchase content from the iTunes Store, App Store, and Book Store, go to Settings > Face ID & Passcode and make sure that iTunes & App Store is turned on. Then follow these steps:

1. Open the iTunes Store, App Store, or Book Store, then tap something that you want to buy.
2. When asked to pay, double-click the side button, then glance at your iPhone or iPad. If you're wearing a face mask that covers your mouth and nose but Face ID with a mask isn't set up, tap Pay with Passcode and enter your passcode instead.
3. Wait for Done and a checkmark to display.

You might be asked to enter your Apple ID password for the first purchase you make in the iTunes Store, App Store, or Book Store."

This Apple Support page has the full details: Use Face ID on your iPhone or iPad Pro - Apple Support

If the issue continues, does it still happen after a normal restart of your device? Do you have any restrictions enabled for your iPhone?

We hope this helps to further isolate and resolve the issue.

Cheers!