App Store asks for billing info for a free app repeatedly, still doesnt download after entering thr info

Your Apple ID likely has an unpaid balance, an expired/incorrect payment method, or a blocked transaction. Update or replace your card under Payment & Shipping, check for unpaid charges at reportaproblem.apple.com, and restart your iPhone. Free apps will not download until billing info is valid.

Read this document about how to view your current payment types and add Apple Account payment methods on an Apple mobile device, a Mac, or a PC --> Add a payment method to your Apple Account - Apple Support

If an item appears in red then it is no longer working and you either need to replace it or get it working again. Even if an app is free, Apple may require the presence of a valid payment method such as a card. You won't be charged but the card has to be there and in working order.