Follow the specific instructions provided in the download package (often involving holding specific buttons while powering on to enter an "Update Mode"). Transfer the file to the radio as instructed.
If after performing a full reset, removing all power, and testing with multiple devices your radio still malfunctions, the issue is hardware-related. Contact Makita customer support for warranty service. Do not waste hours hunting for a phantom download file. makita dmr 112 software update download
: Use a high-quality Micro USB cable to connect the radio's internal port to your PC. Follow the specific instructions provided in the download