| Step | Action | Common Failure | | :--- | :--- | :--- | | 1 | Open Arduino Library Manager | Forgetting to click "Install All Dependencies" | | 2 | Search for your sensor (e.g., "BME280") | Installing a non-Adafruit fork | | 3 | Install the Adafruit version | Accepting the missing dependency warning | | 4 | Look in Arduino/libraries/Adafruit_I2CDevice/ | Finding an empty folder |

If you download just the BME280 library, the Arduino IDE expects to find the chassis inside a folder called Adafruit_I2CDevice .

If you download a BME280 library from 2023 but an I2CDevice library from 2019, you get cryptic errors about missing methods. Delete both folders and re-install the sensor library first, letting the manager fetch the matching I2CDevice.