After failed FW update key not recognised and has solid white LED

When I updated the firmware on my OnlyKey, bought in 2019, it stopped during FW upgrade and the app showed, during flash, “Please connect your Onlykey”. Nothing happened after this. After half an hour I re-plugged the key and it just showed a stable white LED light. The key was not recognized by my Linux and when I touch the keys no LED flashing or anything happens. So I cannot set it to to flash mode because the app does not recognize the key and when pressing key #6 nothing changes, just the solid white LED light.
So my key seems bricked…
Is there any possibility to get it running again?
Tried the legacy upgrade guide, but the key does not react, is probably a newer version not supporting it. Upgrading Firmware From Beta6 to Beta7 | Docs

Can anyone give me a hint, or confirm I cannot “un-brick” it?

The white light indicates it is in bootloader mode and it is ready to load firmware. Are you able to try to load the firmware on a Windows computer?

Ok, thanks for that info and first reply.
Yes I have access to a Windows computer.
Already tried on by business laptop where I have no Admin rights with the portable OnlyKey app.
Here I had once the “luck” that it showed the key was in update mode, but before I was able to select the FW file the App changed and showed “Please connect your OnlyKey”.
After this I tried plugging and unplugging several times , but it did not come back in the “update mode” in the app. Just got an message from Windows that the USB device was not recognized.
Could you pleas give a hint what I can do to get back to the “update mode” or what I need to do to update the FW?
Could also use a Windows Machine with Admin rights or an Apple computer in case this is needed to solve the issue.