How to get it updated, please, preferably without unmounting?
I assume that due to wrong date the sentences are being refused and therefore the FM204 is sleeping.
Hello @Ulrich.S
The device firmware or configuration can be updated directly through the configurator when connected to the laptop via USB cable.
In this case, keep the device connected to the vehicle, use the laptop, configure or update it.
The second option is to over the air, means though fota web. If you have access to the fota web account, the device can be remotely updated.
Regards
Maryam