Pin 10 should be High - but is not the Vcc for the device. Pin 16 is Vcc. @1.21Gigawatts was asking where U3 gets its supply from. The Via near pin 10 is close to the Front Copper track so the connection is hard to see on the PNG.
I took a look at the KiCad files in your repo. There is one thing that I do see.
In Pcbnew, under Dimensions - Pads Mask Clearance, there is a Solder Mask Clearance of 0.2mm. I had an issue where this "default" setting started to expose the copper fill zone and caused some issues. I usually set this value to zero.
Your sensor board does not have any zone fill but your Teensy adaptor board does. Check that that the board is not exposing any more copper than it should. I have to admit, if this were really the issue, I would think there would have been other issues before this one.
What about the other devices on the sensor board? Are you able to read any values from those?
For the Light Dependant Resistor, you could unplug the Sensor board from the Teensy adapter and use the Ohm Meter on your DMM to measure the resistance across pins 15 and 16 of the CE Header. This just verifies at least that system is connected and behaving OK.
Going back to the Teensy board, have you connected a LED and resistor to any of the digital pins on the CE Header to get a "blinky" working? ... just to prove that the Teensy adapter has no issues.