The chipless firmware update was successful.
This Epson printer (WF-3720DWF) (non-US model DWF) can NOT be brought to software update mode by pressing power + top-right of the screen.
If you have firmware newer than CL26H9 - this is firmware compatible with chipless key - then you can bring your WF-3720DWF printer to ROM recovery by official Epson app:
1.Make a normal firmware update using Epson updater
2.Use USB cable to make the update (the printer will allow to re-update multiple times with the latest official firmware)
The printer will not allow to update with previous firmware, that is why you must brick the existing firmware if you want to downgrade
3.There is no step three
4.During the firmware transfer (re-flash the same version) disconnect the USB cable (try this at various points during the transfer)
The ROM will become bricked and next time you start the printer (force shutdown by unplugging AC) it will be forced to start into ROM recovery mode
5.Now you can flash any firmware version you want via USB (including chipless-compatible) and this is the only way to downgrade WF-3720DWF (if needed)
The chipless key can be used after the step 5, while the printer is ON running CL26H9 firmware - this firmware can be found on chipless website
Don't forget to disable automatic software update check in the printer settings and in the Epson software you use on your computer.
I just want to thank chipless for their effort because the cartridges are VERY expensive for this model WF-3720DWF, close to the price of an entire new printer.
Printer cost (brand new) was $140
WF-3720DWF uses EPSON 34/34XL cartriges that cost $99 per pack (XL) and will last only one week in a normal/small office!!!
Do you want to pay $400/mo for WF-3720DWF OEM EPSON inks in you small office?
Or do you want to pay $240/mo for WF-3720DWF aftermarket XL ink cartridges ($60/XL pack)?
Seriously Epson is crazy with these prices, "ripping" small businesses off big time!