The "DVRS Missing" error occurs when the MSU has DVRS enabled in the codeplug but fails to detect the presence of a DVR. This issue could stem from several factors, including loss of power to the DVR, a faulty or loose control or power cable, or an incompatible (Legacy) DVR.

DVRS missing error on the mobile radio, Futurecom, DVRS, APX, XTL, MSU, DVR-LX, VRX-1000, PDR8000, Legacy DVR.

Here are some steps to troubleshoot this error:

• Inspect the Power Source: Verify that the power source (e.g., battery or DC power) supplying power to the DVR is operational. Check for loose connections or damage to the power supply.
• Test Voltage: Use a multimeter to measure the voltage at the DVRS power input terminals. If no voltage is detected, there may be an issue with the power source or the DVR's internal circuitry.
• Check the Power Cable: Examine the power cable for any signs of damage, fraying, or loose connections. Test continuity along the cable using a multimeter to ensure there are no breaks.
• Verify Ground Connection: Ensure that the device has a secure ground connection to the vehicle's chassis. A weak ground connection can prevent the device from receiving power.
• Verify the Fuse: Check if the DVR fuse is blown. Replace it with a new fuse of the same rating if necessary.

If all tests above yield successful results, there's a possibility that the connected DVR is not compatible with the MSU. For instance, a legacy XTL DVR that was never upgraded to support an APX MSU will cause compatibility issues.
To confirm this, use XTL Tweaker software to read the DVR. If you can successfully read the device in XTL Tweaker, it indicates that it is an XTL model and is not compatible with the APX MSU.