There are a few things here that could be possible. Bad laser or DVD key mismatch in the keyvault embedded in the NAND. If it is a laser issue, just replace the laser. If it is a dvd key issue, you will need to RGH the Xbox to grab the CPU key and extract NAND info. Within that NAND info, there will be a DVD key. You take that DVD key and flash it to the drive motherboard using Jungleflasher and a flashing device. I personally use the CR4 XL for RGH, NAND-X to dump the NAND, and X360 USB Pro V2 to flash drive firmware files/replace keys etc. If it is not a laser issue, the only way to grab that key is through the RGH process.
Roughly the cost of grabbing tools like these will be around $100-$120. Modchip Central has a lot of these tools.
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