Hi ChrldambekComunity,
Thank you for using the Apple Support Communities. We understand that you're unable to download the Wallet app on your iPhone after updating to iOS 14.3. We'd be happy to help point you towards a resolution.
First, let's start by going to Settings > General > Language & Region. Confirm your region is set for a location that supports Apple Pay listed here:
Countries and regions that support Apple Pay
If you are in a location that doesn't support Apple Pay, it's expected behavior that you cannot download the Wallet app. If you're unable to download the Wallet app while located in a supported country or region, try these steps next:
If you can’t download or update apps on your iPhone or other Apple device
Take care.