Problems with the Bushido Firmware Update

Hello together,

I would like to update the firmware on my Bushido. I have already looked through the search function, but nothing suitable found.
In the Tacx Training App, the update button is always grayed out and the instructions say that the trainer must not be disconnected from the power supply.
But the Bushido has no external power supply.
I am in despair. What do I have to consider that the update button is activated?

Thank you and happy rides