Re: "Apple Cash transfer issue to bank via Apple Pay"
In addition to the excellent suggestion already from Jeff Donald:
You may need to check you have the newest compatible iOS version installed on your device.
(Updates may include security improvements) You can check in Settings > General > Software Updates.
NB: Before updating, it is always wise to back up the data on your device.
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You can double-check if the method you are using to transfer the funds, is the step-by-step one that Apple suggests: See: Transfer money in Apple Cash to your bank account or debit card - Apple Support
Other info from above article:
"Instant Transfers require you to use the billing address that matches your selected debit card"
"If you're transferring money to a debit card, make sure that it's an eligible debit card.
(ie: Mastercard or Visa debit card in the Wallet app.)
"Make sure you aren't using accents when you enter your name".
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If you need to check whether your device is compatible with Apple Pay:
See: Devices compatible with Apple Pay - Apple Support
Eg: Your iPhone 11 would need Face ID or Touch ID