This phenomenon is due to the high security level of fingerprint payment apps. To ensure the security of your payment, the system is encrypted. After the BL(Bootloader) is unlocked, it will not be able to be used normally. It is recommended that you bring your purchase certificate to the nearest service center to install the official system and lock it back.
Temporary solution:
realme UI 3.0 & above versions: Settings > Search "Payment protection" in the search bar > Payment protection > Turn off the corresponding payment app.
realme UI 2.0 & 1.0: Settings > Security > Payment protection > Turn off the corresponding payment app.
realme UI R & S & Go & T & U Edition: not supported