Here are some common problems with the Godox firmware update:
Firmware file mismatched
Do what you do DO NOT USE A FIRMWARE FILE FOR A DIFFERENT DEVICE. This is a basic principle of all firmware updates: the firmware is closely linked to the hardware configurations, and any Differences in hardware can mean joining a device if it overwrites the wrong firmware image.
While a TT685 and a V860II may be identical in IU and features, the fact that they both use different power supplies means that the firmware images are not identical. Each device has its own firmware file for a reason. Users of the TT350 found this way difficult when Adorama mistakenly published the TT350-do Update (specifically to add compatibility with some newer EOS M bodies) as a generic TT350 update. So many owners who were not Canon TT350 were left with their flashes with this update, Godox finally published the initial versions of the TT350 firmware.
If your device does not yet have a published firmware update, aspire it and wait until he does.
The only way to correct a mismatch like this is to reload the appropriate firmware image, but this depends on the device being able to recognize the firmware update request, and sometimes the correct / current firmware image that you need not available. Requesting the firmware from your distributor or Godox may be your only recourse.
G1, G2 or G3
Godox has three separate firmware update applications. G1 is for pre-AD200 devices; G2 is for AD200 and later devices; G3 is for AD400 Pro and later devices. Check the Godox download page to make sure you are using the correct application for your device. Both applications, when installed, must also install a custom USB driver.
Cable and port
Make sure you are using the correct cable for the device. Newer devices (for example, A1, Xpro, R2 Pro II, AD400 Pro, X2T) use a USB-C cable, while older devices (for example, TT685, V860II, AD200) use a micro USB cable. If you are upgrading an AD200, AD360II or AD600, make sure you are using the micro USB port, not the USB-A port that is for connecting an FTR16 receiver if you want to use Godox's oldest 433 MHz radio system.
If you are using a micro USB cable and the G1 / G2 software does not recognize the device, consider testing a different cable. Some micro USB cables are used only for charging and do not transfer data.
If you downloaded your files from the Godox site, instead of Flashpoint, the paths for updates or applications may contain two-byte Chinese characters that may cause an error. Deleting the two-byte characters solves the problem.
The downloaded file is a .rar file that contains the firmware update file and a PDF that contains the firmware revision history. If Internet Explorer has changed its name as a .man file and does not have tools to extract the contents of the file, you can simply rename it to .rar.
In addition, the .rar format has changed in recent updates, so you should simply update your file application (for example, update Winzip to the latest version). Or you can use the latest version of open source 7Zip.
Disable the driver signature
Someone in dpreview mentions that you may also need to disable the driver signature for the updater to work.
See also: Flash Havoc article about the G1 application.