After updating:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.btcontract.walletfiat/com.btcontract.walletfiat.MainActivity}: java.lang.IllegalArgumentException: com.btcontract.walletfiat: Targeting S+ (version 31 and above) requires that one of FLAG_IMMUTABLE or FLAG_MUTABLE be specified when creating a PendingIntent. Strongly consider using FLAG_IMMUTABLE, only use FLAG_MUTABLE if some functionality depends on the PendingIntent being mutable, e.g. if it needs to be used with inline replies or bubbles. at at at at