MS5611 Barometer not working on PCB design
Looks like you have your MS5611 hooked up correctly, with CSB pulled low and PS pulled high. The two sensors also do have distinct I2C addresses. The following is just a guess without looking into the Atmega 32u4, but I have had trouble interfacing 3.3V devices to Atmega processors because of internal pullup resistors which drag the I2C up to 5V. On some boards this can be disabled in code, but on others I have solved this with a level converter on the SDA/SCL lines.