Well, if I2C is enabled within Raspbian, AND your wiring is correct, AND you’ve installed the Adafruit library- AND the Adafruit can’t see the I2C device, -then it’s dead…
I’d reinstall a fresh Raspbian and get that all setup and updated, enable your expanded memory and your I/O options, then install your I2C utilities. Really, if the Adafruit utility can’t see the I2C @ 0x40 (the default), it could be software, hardware, firmware…you name it.
Going off of what @HighTech said, you might also want to check the ribbon cable that’s attached to the Pi-side of things. Make sure it is not attached the wrong way. If I told you’d I’ve never done this I’d be lying!
Keep us posted with your progress, BMP180 is a super easy sensor to add to Cayenne, assuming all wiring and the hardware itself works of course.
It’s a very good call, I am a total beginner and not above putting things in upside down! The ribbon cable from the image above - The black wire on the right of the image is attached to the end of the GPIO furthest away from the USB ports. If you look at the image on this link (https://goo.gl/images/dGOMc7) the back would go to the top of the picture.
I’m very happy to install a fresh image, I was using the image which came with the pi kit. Could somebody who has a working system perhaps recommend a good download for an image with the right components pre-installed?