Dear Nivas,
in most cases the error FZ003 appears if you create a payment proposal for some payment ID, date; then leave it as is; then create another payment ID, date and execute payment proposal generation.
Accounts are blocked in the first payment proposal.
This is a standard system behaviour.
Please ensure that the account is unblocked i.e. delete unsuccessful or incomplete payment proposals or execute the payment run to its end so that the accounts do not get blocked.
You can check the SAP note 1786450 for more information.
Also, this issue may be caused by account configuration.
In case your account is a reconciliation account, check it flag 'without payment transaction' is set.
This flag means: Reconciliation account not relevant for auto. payments Indicator that the corresponding reconciliation account is not taken into consideration with automatic payment transactions.
Best regards,
Vera