Just bought a 2nd hand OP-Z and noticed that it was running an old Firmware.
I have managed to connect it to an iPhone/iPad, just fine over Bluetooth, and confirmed that the USB charging cable is charging it ok.
However, when I follow the instructions to upgrade the firmware (Hold down Screen button, power on, wait for flashing white dot), then plug in the OP-Z to the Mac, no drive is mounted.
I’ve also run the Factory Reset, and still the OP-Z doesn’t mount when entering Firmware Upgrade mode.
put op-z FIRST in disk mode. and THAN plug it into the computer. in that order.
Yep tried that, no dice sadly 
wondering if it’s a macOS issue, running Big Sur on Apple M1 chip.
I have same issue. No disk mode. Works in windows on the same MacBook
Ah sweet, good to know I’m not alone!… so seems like a macOS issue.
Wonder if the TE folks are aware of this?
It could be M1 chip actually in combination with USB 3.0 protocol. The way mounting works (in firmware or disk mode) is a little bit strange and not consistent. On my computer one USB port accepts only disk mode and other USB port accepts only firmware mode.
Try connecting to different computer and if it still doesn’t work than its a broken op-z.
you can also mount it straight to your iPhone and use files app, if you have a right cable.
Phew! So turns out I seemed to have a dud USB cable (the original TE USB-C OP-Z one)…
Tried a different USB-C cable and it’s now showing up, on Mac and Windows.
Good that you got it handled. I tried two different usb-c cables, original usb-c-a to c-a adapter on MacBook and two other usb-c-a cables to adapter. The Z exits content mode intermittently. Tried connecting after entering disk mode as well. Doesn’t show any sign of connection in diskutil either. No problem in windows on same computer. Doesn’t show in iOS or iPadOS either but Z-app works. Update mode works in macOS.
Starting to think I made an error somehow when I renamed disks and made partitions on external drives with diskutil a while back. What’s the Z disk mode partition’s name, device id and file format suppose to be? I’m thinking I can make sure it’s correct through windows since it can access it. Yes I’m desperate
Silly question but have you tried a factory reset? Wondering if that could sort things?
‘OP-Z’ is the volume name that shows up in Disk Utility,
File system: MS-DOS (FAT12)
Volume Capacity: 39,813,120
Available Space: 39,616,512
Media name: teenage OP-Z Disk Media
Yes I have. Reset and reinstall os I’ve done something to mess it up because I can’t be the only one trying to enter disk mode with macOS Big Sur