After run “$ sudo dpkg -i cumulocity-rpi-agent-latest.deb” I get the error message: “it´s not an archives in Debian format”
have you followed the same procedure mentioned in the https://cumulocity.com/guides/devices/raspberry-pi/
I have followed the above documentation and was able to successfully register the rasperry pi with cumulocity cloud.
is there any chance that you attach the device logs of your Raspberry Pi? This would help to see what is going wrong. Also it would be great to know on which tenant you are trying to register the device.