I've encountered the same issue after installing flirc gen1 on my new device after a while of not using it.
Flirc-Setup-3.25.4.exe does not install the driver so I installed the old one from the sticky topic.
Flirc-Setup-3.25.2.exe installs fine but the old issue with inability to update firmware 3.11 -> 3.12 popped up back again
Flirc-Setup-3.25.4.exe installed on top makes flirc unrecognisable again. This is a mess with a long history.
Is there a chance to finally sort it out?
Here is the link to the firmware problem: