Hey, guys! I had the very same problems yesterday with my POD HD 500. I managed to solve it. Hopefully, it will help you, as well.
WHAT HAPPENED:
I bought a second-hand POD HD 500 unit which was perfectly working but had a bunch of user's presets which I wanted to remove all at once. The unit had firmware v2.62 installed. So to remove all presets I pressed "Reinstall latest" firmware in Line 6 Monkey and selected not to preserve my current presets there. The latest software currently is v 2.62, so it is the same version that was installed on the unit.
ISSUE:
The software re-installation failed with the error: "(code 80007211) Firmware update timed out waiting for a response from the device.". Then after several attempts to re-install the firmware, I ended up in the situation when the unit and was constantly displaying "UPDATE FLASH". I tried 2 different laptops (MacOS and Windows 10) and different versions of firmware. Then I downgraded to v 2.32 first (which worked) and the tried to install v 2.62 again. This last attempt to re-install the firmware made it even worse. The unit was working, but when I tried to change preset from "Son of Plexi", the unit froze and was not responding to anything. Another problem was that Monkey showed firmware version as "Unknown". The POD HD 500 Edit was saying that it needs a unit with software 1.30 or above to work and refused to work with the POD.
I also tried to boot the device with pressed left nav button. Did not help. The device was, basically, unusable.
MY SOLUTION:
I called Line 6 support. After some time of analysis the guy from the support suggested the following:
1) Press down nav button,
2) Unplug the power cable from the POD,
3) Plug in the power cable while holding the down nav button,
Now the unit was displaying UPDATE FLASH again
4) Connect unit via USB to the laptop,
5) Close Monkey (if opened) and open it again,
Monkey now identified the firmware version as v2.62 again
6) Reinstall the latest firmware.
This procedure did not work for the first time and failed after about 15% was completed. However, the guy suggested to try once again and see if it will move further.
He also said that if it will not work, but the progress will go further, we need to try again and again. Presumably, the current firmware on the unit is corrupted.
However, after the second attempt, the firmware was finally re-installed and after that, the unit came back to the normal working state.
AFTERMATH:
1) The support guy was pretty surprised with the issue and said that it is super strange behavior. Even though, many people have very similar problems with this unit. Previously I had an HD 300 unit for about 6 years and never had this kind of problem with it. Same with my Variax guitar. Seems like there is some serious problem with HD 500 because I was able to find many people on forums having the same (or similar) problem with no clue how to fix it.
2) The guy from the support was super helpful and really tried to fix the problem. Big appreciation to him for this attitude.
3) If you have this kind of problems and run out of clues - call the support phone line. As you can see, they can help you with your problem via phone. However, waiting time in my case was about 25 minutes.
P.S. I just noticed that 'wilsonmartins' also suggested solving the problem by pressing down the nav button. So, one more confirmation for this solution :)
