DFU Update says zip file not supported

[rider]

I'm trying to apply a firmware update using a zip file that has worked with older version of nRF Toolbox. Using the current version, (4.1.1) on iOS, I select DFU, then select my zip file under User Files. When I press Done, I get a popup saying "DFU -- Selected file is not supported".

Any ideas what to do? It's not my file, and I didn't have any development role, so I'm just trying to figure out how to apply the update.

Any help would be really appreciated.

The zip file: IRT_V2_REV_A1_C_1_0_39.zip

[rider]

I gave the hex file a try. After putting the controller into DFU update mode, I selected the file (the hex application file) and selected the device ("IRT DFU").

I think I'm supposed to get a "start update" button, or something like that, but instead, It stays on the "DEFAULT DFU" screen.

The only available action (as far as I can tell) is pressing a link marked "U...ad" under "DEVICE FIRMWARE UPDATE". This results in a message saying "DFU - The init packet is required by the target device".

I Googled for this error, and there is some chatter that newer SDK versions require additional files in the zip, and that hex only updates won't work. Not sure if this makes it a dead end, since I don't have the code or platform.

Any more ideas - I'm game to try them.

Thanks