After a dispense attempt, if the machine displays 'Out of cash' and the transaction logs show a Puloon error 64 or 67, then your dispenser is not detecting a cassette properly. This would indicate that perhaps there is blockage or debris covering one or many of its sensors.
Code 64 refers to the top cassette (#1), while 67 refers to the bottom cassette (#2).
Inspect the sensors of the cassette and its bay for any sort of blockage or debris, and clean up if there is anything there.
The cassette's sensors can be found on the mouth of the cassette, and on the front left-hand side of the cassette:
Inside the scanning bay you'll find sensors on the right-hand side of the cassette bay; these are to interact with the cassette's side-sensors metioned above:
Once all of the above sensors have been cleared of debris or blockage, re-insert the cassette and perform a test transaction.
If a dispenser error message is present in the transaction logs, the transaction is already marked as 'redeemed' and is unable to be attempted a second time. Therefore, you may reconcile with the customer by manually refunding the equivalent undispensed amount in crypto or fiat.
For a full report on the transaction status, export the transaction spreadsheets and consult both the cash-out-txs and cash-out-actions, the latter of which records the dispense events including the amount of successfully dispensed notes from each cassette for particular transactions.