@WickedFog , thanks for a rude awakening this morning out of my needed sleep

Well with that
I never tried to update my 4gs radio, I only did my RC8X. With that updating is completely different, I don't know about the update process on the 4gs as I never done it.
If your on Facebook, join the RadioLink Official Group/ Support Group and see if anyone else can help.
Or search RC4GS updating on YouTube and try to follow that.
I had to do this with my rc8x before, the radio was in a blank / test screen just like yours. What I did is wiped both the internal and external drives on the radio (as the radio (RC8X) has a SD card built in). I did this by formatting the drives (if your on Windows PC) and I re installed the update on to the radio. Note that you have to install the complete file packs, not the fixed packs for doing this as you just wiped the drives. And also note by doing this, you are essentially wiping the model memory and all of your saved settings so you would have to go back in to redo them. And then after doing all of that, it was back to normal. Not sure if the process is the same but
Little backstory on my RC8X firmware updating, I updated to 1.1.8 like 6 months ago I think, started having issues with cutting out, freezing and fail safe not working. Updated to the current (at the time) 1.2.0 and still had issues. With that a group of people in the Facebook group had the same issues so we all got together and figured out how to downgrade on the updates. By wiping the drives and re installing the update you want to install. With that, everyone figured out 1.1.5 was the latest good update with no issues. Now a couple days ago, they released 1.2.1 and I'm Awaiting reviews until I update it.
I'll pop on the interwebs and see if I can find anything. But essentially wiping the drive and reinstalling it like new should be able to fix that blank screen.