Customer Bank Account Setup issue at customer site level

Scenario:
When the user attempts to create a bank account from the Payment Details section at the Customer Site level, they encounter the error:
"A record with this combination of values already exists."

Action Taken:
We advised the user to select the option "Add an Existing Bank Account to this payer" and search using the account number. However, the account is not appearing under the Customer Site level.

Request:
How can we resolve this issue quickly? Please suggest possible solutions or steps to successfully add the bank account.

Thanks,

Reshma A