Perhaps you should read the thread. OP states that this was an EU carrier and departing from the EU. It does not matter what the COC provides. The law on this is very clear.

EC 261/2004 permits the passenger the option of a refund and places the responsibility on the operating carrier.

To be clear, this does not absolve the TA of liability. It simply places the responsibility of coordinating all of this on the operating carrier so that the passenger doesn't have to run around and figure it out.

One thing is clear. Don't wait. There may be time limits for initiating a chargeback depending on the country. If your request for a refund is not timely honored, start the chargeback dispute process. These are time-consuming and costly and all of those are ultimately at the merchant vendor, e.g. air carrier / TA's expense.