If official sites are inaccessible, use driverpack.io or snappy-driver-installer.org with caution. Only download the exact driver matching "USB\VID_0403&PID_6001" (the hardware ID for FTDI).
Connection drops or "Hardware Not Found" errors in the diagnostic software. Failure to update the firmware on the diagnostic interface. Where to Find the Driver Download Delphi 100 251 Rev 1.0 Driver Download
To protect your PC and data, these sources: If official sites are inaccessible, use driverpack
If you continue to experience issues, consider that your Rev 1.0 hardware may be faulty. Replacement units (Rev 2.0 or newer) are affordable on eBay and Amazon, but your existing driver knowledge will still apply. Failure to update the firmware on the diagnostic interface
The Delphi 100 251 Rev 1.0 does not work on macOS or ARM-based Windows (Surface Pro X, etc.).
You can manually point the Windows Device Manager to this folder to install the driver. 3. FTDI Official Site