I was able to get the Adafruit Ultimate GPS to work but initially ran into the same issues you see. My issue seemed to be linked to noise / sag on the Electron’s 3.3V output. I could never get a fix when I was powering the GPS from the Electron but, when I powered the GPS directly from the LiPo battery, it worked like a charm.
In fact, this is a quote from the Adafruit tutorial on this product: VIN - power input, connect to 3-5VDC. It’s important to connect to a clean and quiet power supply. GPS’s are very sensitive, so you want a nice and quiet power supply. Don’t connect to a switching supply if you can avoid it, an LDO will be less noisy!
So, I think the switched power supply on the Electron is too noisy.
Here is a link to the guide I published, happy to share more.
Chip