Firmware update failure

Suggestions, please!
I have done the latest firmware updates (with no problems at all) for the K-70 and K-3, following the Ricoh instructions to the letter. I then attempted to do the same for my K-1 - downloaded the firmware file; copied it to the root directory on a newly-formatted SD card, put a fully-charged battery into the camera followed by the SD card and switched on while pressing the Menu button. In short, exactly the process followed for the other two cameras. However, the K-1 ignored the Menu press and simply opened up as normal, ready to shoot. I have tried different SD cards, each one formatted and with the firmware file correctly copied, all to no avail. For what it's worth the current firmware on the K-1 is V 1.52 and the latest is V 1.54.
Any ideas?
Thanks,

Unzipped it first?

K1 or K1 MKII?

That's all I can think of.

Dunno, did you empty both card slots and just use one for the update?

Thanks for your prompt responses. I just went through the whole process again, following the Ricoh instructions but with a different SD card and this time it worked fine!

No idea why it failed with the first 3 SD cards as they were all prepared in exactly the same way as the fourth, so a bit of a mystery.

Nevertheless, thanks for responding!

May not be relevant but only slot 1 will allow the update to work.

Thanks for that, Peter.
However, I’m pretty sure that I removed both SD cards before reinserting and reformatting just one in slot 1, then took it out again, downloaded the firmware file to it and put it back into the same slot.