my macbook location can't be determined.

PS -- Go into iCloud in System Preferences and make sure that Find My Mac is checked. Mine used to be, but somehow the check mark disappeared, possibly when I recently upgraded to High Sierra, which wiped out numerous settings (another Apple irritation; they could at least warn us). Re-checking the box made the Macbook Pro findable again -- it was saying it was offline previously.

Sort of. Find my iPhone on iCloud now locates one of my Macbooks, but not the other. (If iCloud can't find your Macbook Air, call Apple immediately, because this is a vital service you need.) Apple Maps -- an often irritatingly inaccurate program -- also finds whichever Macbook I'm using. Google Maps, which after years of pinpoint accuracy suddenly had my location wrong by 40 miles, is now mysteriously within one mile. There are so many variables -- Apple, Google, IPS, modem, router, triangulating towers -- that I've quit trying. (The two reply posts from 1/20 weren't helpful. The explanation about location services is circular: doesn't explain why Apple doesn't know my AP location. As for the other, about setting the time zone manually, that was my normal configuration. I've tried it both ways, manually and automatically, same results.) Good luck.