I'm beginning to suspect that GarminCure3.exe is not processing some of the aera's GCD's non-standard BIN files correctly, resulting in Updater.exe not being able to properly flash some regions when 136401000560.RGN is attempted to be loaded. To eliminate that possibility let's try using QuickCure3 instead. It uses only a modified generic boot.bin as an RGN and it might work to re-enable Mass Storage Mode. It can't harm anything even if it doesn't work so it's very safe to try. Check behind the spoiler below:
Spoiler: Click
[Only registered and activated users can see links. ]
Please follow these steps:
  • Open the above ZIP file somewhere convenient to find the folder QuickCure3 containing 136401000560.rgn and Updater.exe.
  • Drag the RGN onto Updater.exe to open its GUI
  • Select the radio button next to "USB Device" on Updater's GUI and leave it visible on your Desktop screen
  • Plug a 'known-good' USB cable into a USB2 port of your PC/laptop
  • Put the aera into preboot by holding it's screen and then plug the cable into its socket to power it on
  • IMMEDIATELY you see the device's details in the box adjacent to USB Device on Updater's GUI, click OK or just hit the Enter key on the PC keyboard and keep holding the device screen until Updater finishes by reporting .... hopefully a 'success' message not another error like before.

If it reports with a success message, release the screen and check if it's now seen in Windows Explorer.

Let me know the result and we'll go further. Don't despair if Quickcure doesn't work, we can try other things still. Provided the device doesn't have a hardware failure we can fix it eventually i'm sure.