Hello, in getting that error what you can do if you haven’t already is to re flash the library firmware to ensure that it sees it correctly throughout the unit.  That should make it so if there is a part that is missing or corrupt that it will repair it.  Here is a link to download the firmware just in case you don’t have it. www.dell.com/.../DriverFileFormats  Let us know how it goes
The following is from RMC: Is there any Firmware upgrades that I am missing? How do fix the error message?
My 128T Displays: Upgrade Library Firmware