I have a similar problem. It's April 2020. I recently got out my JM4 again & tried to update the firmware to 2.09. I copied the wavs I had on the SD card elsewhere to preserve them.
I successfully downloaded the fw.bin file & downloaded the Line 6 Monkey from your website. When I open the Monkey the JM4 isn't listed on the dropdown menu & I can't go any further. I tried opening the fw.bin & got a file fw.bin.cpgz. I get another file, fw 2.bin when I open the cpgz file. When I open the fw 2.bin file, I get a fw 2.bin.cpgz file. Opening that, I get fw 2 2.bin file, which reveals a fw 2 2.bin.cpgz file. I'm pessimistic that If I open further files. I'll continue to get progressively smaller files that I'll have to open. Uncle. I give up. It's like I'm trying to open a Matryoshka doll with no end in sight.
I don't see "update from file" anywhere. My JM4 doesn't have a USB port, so I suspect I'll have to update it via the SD card. Please advise me on what to do next. How do I use the Monkey if my device isn't listed, or is there another way to update the firmware?
