Hi @duerstad It seems you have two issues.
(a) the eCO2 and tVOC sensors not being enabled
(b) the PM sensor apparently not operating.
In SCK 2.1 these sensors both connect via the Urban board; which is plugged onto the Data Board via a 16 pin connector.
The below advice is obvious to someone that is technically trained and maybe you have already gone through the recommended checks but just in case I have provided it below.
In my own experience; I have found that it is possible for the Urban board sensors to be apparently working but the CCS811 eCO2 and tVOC sensor not recognised; and the PM sensor also affected.
What I found was that the Urban Board was not properly seated onto the Data Board.
It ‘appeared’ to be connected properly; but in fact there was a tilt on the board and this caused a very slight gap (<0.5 mm) to appear on the outer side of the connector. when I straightened the board and made the connector sit flush on both side; then the CCS 811 sensor started working. (The SCK2.1 needed to be rebooted of course.)
Along similar lines; it’s also possible for one or more pins on that 16 pin connector to become bent; so that it does not go into the female receptacle properly. It can cause the same symptoms.
Also; it is possible for dust or debris to affect the pins on this connector.
So; I recommend that you:
(a) remove power from the SCK; including the battery.
(b) disconnect the Urban board; examine it closely for any damage. The PCB tracks are mostly covered by laminations; but if there is damage to the board then maybe it is visible as a line or a crack.
(c) examine closely (magnifying glass and strong light) the connector on both board.
(d) straighten any bent pins; remove any debris etc as may be necessary
(e) replace the Urban board onto the connector; make certain that every pin goes into appropriate socket and that the Urban board sits in a parallel plane to the data board.
Also check that the 8 pin cable going to the PM sensor is properly seated at both ends[
(f) Plug usb and battery back in; connect USB to computer and engage Arduino CC and open the monitor screen.
(g) observe closely the text displayed on the terminal and what the various messages say during the boot up.
then run through the sensors and i2c command and see if the ccs811 and pm devices are now recognised and (after a delay) deliver readings.
Note that CCS811 sometimes takes a few minutes to deliver readings; as does the PM sensor. So; give it 5 mins or so whilst observing the sensors output on the Arduino Monitor display.
I do not know where you are in the world; but $100 for shipping seems excessive to me. May I suggest that you look at both UPS and Fedex; one of them will be cheaper than the other. I would expect to pay no more than USD$50 and probably less.
Did you purchase the kit direct from Seeed Studios in Shenzhen/HongKong or did you purchase through Mouser/Digikey ? Have you contacted them and requested a Return Material authorisation ? If you have that and they say your freight cost will be reimbursed then I think you can rely on it.