I have an HGLRC Titan Plus F460 Stack https://tinyurl.com/sby43he for my quad drone and I seem to have trouble updating the firmware. I try using the firmware flasher and either the OMINBUSF4 (AIRB) or the OMNIBUSF4(Legacy). both seem to not work. I even try holding down the boot button and then plugging it in and then letting it go, then try Flashing the Firmware but that does not seem to work. It keeps giving me the "No response from the bootloader, programming: FAILED" every time. PLEASE HELP this is my first drone and I don't know if I'm doing this right. Am I supposed to have the battery plugged in when I do this?
No battery needed except when you are driving the motors or if your receiver needs battery power (not powered off the FC). You hold the boot pin while plugging in USB to get the FC into dfu mode then should be able to flash, try selecting full chip erase option or the auto flash on connect options some FCs are more touchy about how the flashing procedure happens.
Are you able to connect normally not in firmware flashing mode just in config mode? If config mode works the serial port is good and drivers are good, if can't connect maybe need to install the USB serial drivers first see the help on the betaflight launch screen for those drivers.