I Was Unable to Use My Open Ticket on Turkish Airlines

I had opened my ticket number 235...33 in the last week of June 2023. However, when I called customer service on 21/09/2023 to use this open ticket for an Ankara-Istanbul economy class flight, I was informed that I could not use my open ticket. The customer representative mentioned that it could be a system error and advised me to provide feedback. After a 40-minute conversation with three different customer representatives, I am still waiting for a response regarding why the ticketing process was incomplete and why I couldn't use my open ticket. I don't understand why I have to follow up on this issue when it is not my fault. I cannot use my open ticket, and nobody knows why. I wish good luck to your representatives who suggest solving non-customer-related problems through feedback.