Turkish Airlines Elite Plus Membership Benefits Not Honored

I am an Elite Plus member of Turkish Airlines. My membership benefits include business class upgrade rights. When I requested a business upgrade from Turkish Airlines, they informed me that there was no availability for the requested flight. However, when I tried to make a paid upgrade, they said there was availability. Despite my efforts for days, I couldn't complete the process. Even though I am an Elite Plus member, they never allow us to use our rights. I will provide much more detailed visuals and also explain with a video regarding the issue. They do not allow us to use our free upgrade rights by saying there is availability for a paid upgrade. Despite visiting the Turkish Airlines sales office and repeatedly calling customer service, they do not provide any solution.