CADMV claims on their web site that they cannot accept a P.O. box as a residence address. I have yet to find anything in California state law supporting this policy, though IANAL. Their enforcement seems to be quite lax.
DPVCMRA = delivery point is a commercial mail receiving agent. Any sort of location with PO Boxes.
https://developers.usps.com/addressesv3#tag/Resources/operat...
Disclaimer: I used to work for my state's DMV.