Been tying for the last hour to update the OS from 1.21B to 1.22.
Have updated the OS three times before with no hassle but now for some reason C6 does not see the A4 in the ‘config’ menu.
I have set the MIDI ports on the A4 to USB.
When the A4 is in normal mode, C6 can see the A4 but not when trying to update. Overbidge is working fine also so there is no problem with the USB.
What on earth can be wrong or is there a workaround?
not clear from your post, but switch out of overbridge mode when using C6 if not already
I can’t seem to make it happen, either. I’m out of OB mode, correct ports chosen in C6, midi ports set to usb only on AK, still no love. Tried it many times and exhausted all troubleshooting avenues I’m aware of. My problem is with an AK. I had no problem with AR or A4.
I’m upgrading from 1.21 to 1.22C.
Anybody? Very frustrating.
What a bummer - sounds like everything is set up properly… it worked for me when I had the Elektron device selected in both In and Out Interface menus, and SDS Handshake enabled.
Also, make sure you highlight/select the sysex file(s) before you initiate the transfer. Hope this helps…
Had the same problem, using AK.
Managed to get it working by disabling “Turbo” mode in C6 and restarting AK. Then selected the file by “Upload” instead of drag n drop.
I thought there was something way wrong with usb settings but I got it working this way. Transfer was very slow but worth it :).
Hope you get it working!
@Avanttronica, I only mentioned OB to show that the connection between the A4 and the computer was okay. I wasn’t in OB mode when trying to send the new OS. Thanks anyway. This problem is very frustrating. 
Good to know that I’m not the only one though…
I eventually got it to work. Was late at night after many tries and unfortunately I didn’t document which changes made it happen…did a victory dance then promptly slept. I suspect it may have been a file path problem, as dobermate said.
Good luck, EndaGeorge, hang in there!
Just curious, anybody else have trouble deleting files from C6? I have to quit the app and reopen it to remove a file. OSX 10.10
Highlighting the file, and clicking “Close” in the menu above doesn’t work?
Okay - eventually got it to work by selecting ‘OS upgrade’ from the global menu. Thanks. 
Sorry to be bringing up such an old post but I have the same problem… Upgrading my A4 mk1 from OS 1.22 to 1.35B using C6.
Every computer recognises the A4. I’m able to sequence it using Ableton Live and I’ve already successfully tried to send sysex sound banks to the A4 with C6.
A4 doesn’t go past “OS Upgrade - Waiting for sysex”. Other than that it works perfectly.
Any ideas on what might be the cause of this?
Thanks!
EDIT: Also tried doing everything with a MIDI cable instead with the proper settings to no success as well…
Have you tried using SysEx Librarian? It always works and no fuss or cost for OS X.
Thanks for the input. Just did but AN4 is “waiting for sysex” as well
Is the A4 waiting for sysex before you start sending it?
Yes, I put it in OS Upgrade mode before I start sending the sysex file. I’ve actually just managed to upload 1.24C in the exact same way. I’m still waiting for it to finish. It’s weird… maybe 1.35B needs a more recent firmware to be upgrade from… Once it’s done I’ll try to upload 1.35B and see how it goes
Ok, not sure why but it did work like this. I’m now able to upgrade to 1.35B. Thanks!