Unfortunately, in most cases of a failed update, the firmware is corrupted which actually causes hardware damage to the memory chips inside and typically cannot be fixed.
Unplug power to the receiver for an hour, then attempt the factory reset again (init all, from the advanced menu).
From there, attempt the firmware recovery via usb again.
If still no change, that would confirm hardware damage, and the unit would have to go in for factory service to be recovered. They will attempt to reflash the system, but usually end up having to replace the main board in the receiver. Even though this is a 2015 model and should still be under the factory warranty, if they determine the issue to be caused by a failed update that was not their fault (not a corrupted file, but rather a power or network interruption on your end) they will not cover it, and repairs will not be feasible, as that new board will cost you about $550 to replace, which would be better spent on a new receiver with a fresh warranty at that point.
Best regards, ***** ***** for the news,
I am an independent technician and I've spent my personal time, unpaid, in an effort to assist with the question for which you solicited my services. This site works on the honor system, and to that end, I have prioritized working with you ahead of other paying customers.
Although you’ve already paid your fee to the site, I am only compensated for my efforts when customers such as yourself leave positive feedback for my work. Again I apologize there is not a better outcome here, though this is really beyond either of our control. I do hope you’ll consider leaving a 5 star rating for me, rather than “shoot the messenger”, so that I may get credit for my time spent in good faith to answer your question accurately. Rating 1 or 2, or not rating at all, does not produce a refund, it only penalizes me for trying to help.