Why does the HDD indicator always turn red, with the failure of installing TOS?

This is probably because there is no TerraMaster system file in the hard drive, causing the TNAS device to fail to start normally. Please power off your TNAS, remove all the hard drives and other external USB drives connected to your TNAS, reboot NAS, and then reinstall all the hard drives after about two minutes. Please try to search for TNAS again using the TNAS PC desktop application.