Orange LED blinking on first use means the hardware is almost certainly good. The last test done on each board at PJRC is programming the LED link using a USB cable, so it definitely did pass all the hardware tests.
Very difficult to help when I can't tell what you're actually trying and what you're really seeing. Can't even tell from this message if you're using Linux, MacOS or Windows.
Even though you said you're tried all troubleshooting, I'd recommend getting Teensy Loader on your screen and turn off Auto mode (any Verify or Upload in Arduino turns it back on). With Auto mode turned off, keep that little window visible. Then hold the pushbutton on your Teensy while you plug in the USB cable. Release the button after the cable is fully mated. Hopefully the Teensy Loader window will detect the hardware.