It seems it started working now.
However, when I try to add a update to a device that has not yet registered to RMS, I am getting this response:
"message": "File '[omitted].tar.gz' is incompatible with device's (CarstenTest) model or firmware version."
I realize that RMS does at that time not know if the configuration will indeed fit for the device I am trying to add it to. It would be super super helpful, if RMS could detect the device model by the serial number upon adding it, so adding an update becomes possible.
We are dealing with scaling up provisioning thousands of Teltonika RUT240, and we really need a good way to scale this. This option would help us massively.