Wireless Joint

Hello friends. I finally found a topic on the forum as I wanted. A few weeks ago I bought a second-hand netgear m5, namely 5200, from Facebook market. Although I have been trying the product for weeks, it does not see the SIM card. More precisely, when I insert the SIM card or insert different SIM cards, when I enter the manual settings from the computer, it sees the networks inside the modem, but when I try to select the networks, it does not accept them. The screen says sim card not installed. I talked to customer service and they want something like an invoice. I say let me have it done for a fee and pay for it, it still does not accept it. The product is brand new, I think the guy I bought it from scammed me, I do not know. How can we remake this device? Or I need to adjust my motherboard completely, no matter what I do, it does not work. Please help me. Let's flash it if it needs to be flashed. I need professional friends on this subject. If we can solve this problem, of course I can pay the fee to the friend who helps. I use it in Hungary, in Europe. Or if there are friends who have the same problems, what did they do as a solution or how can I get this device back into operation? Thank you very much in advance and have a good day.