This has been a common problem . You will need to use the latest version of the standalone VEXos firmware update utility and make sure any other programs like VCS are closed.
More details could be found in this thread:
Just grab the standalone V5 firmware updater from here, it will probably detect invalid assets and allow update.
VEX Robotics – 13 Jul 16
VEXos (Firmware)
If that doesn’t work, select the force update option after following the instructions below for showing the advanced options.
More info here:
Our students briefly saw that red screen while updating the firmware yesterday.
They fixed it by turning the v5 controller off and on, then the Brain asked to perform the firmware update on the controller. Once the firmware update was done, everything was good.
Have you updated the firmware to version 1.0.2?
Finally, you may want to switch from VCS to a newer VEXcode programming environment:
As most people have noticed by now, it’s been a while since the last update to VEX Coding Studio. We understand your frustration, but due to some unforeseen issues the next release is still not quite ready for the public.
That being said, we’ve heard many of your concerns. We’re happy to announce that we’ve been working with Robomatter to create a new, text-only programming software named VEXcode. We have realized that many of the advanced text editing features that our users need do not fit in…