FedEx Commercial Delay - Four Pallets Stuck In Customs

My commercial shipment with tracking number 885191222031, sent from Belgium to Istanbul, has not been delivered to me since October 15, 2025. FedEx claims there is a missing document, but I have not been asked to provide any missing paperwork. Moreover, I was never informed about which document is supposedly missing. I have tried multiple times to contact FedEx customer service regarding this issue, but no one has been helpful or provided a clear response. The shipment consists of four large pallets containing valuable materials that must be delivered to my customer. Due to this delay, I am experiencing serious issues in my business and customer satisfaction. I urgently request that FedEx resolve the problem with my shipment or provide me with the contact information of the responsible staff handling this case.