Wow, thank you both for the help!
@gusgonnet I found this from the search: Photon: SGP30 Sensor not found, which seems very like the problem I’m encountering. I had a couple of questions about that though. In that, OP said he used “the I2C debug”. How can I use that?
Also, someone seemed to solve it with: Photon: SGP30 Sensor not found - #3 by ScruffR. I am just not sure what he is talking about to be honest. How would I send the 0x0020? Do I need to go in and change the library myself? My C++ is fairly rusty.
@dreamER I am actually not using a breakout board at all. I made a PCB with the voltage regulator and i2c level shifter, to bring the 1.8V SCL and SDA lines up to the 3.3V bus. Also, I have tried soldering in different resistors in parallel with the 20k pullups I already have on the board. Everything from a 1k to a 50k in parallel, and none of them improved the functionality. I do have 4.7k pull ups from the 1.8V i2c lines though, as shown below. I’m not sure what else to try with regards to the pull-ups.
Thanks again! Super duper helpful