After updating to Mojave some location functions were not working despite being enabled i.e. the precise location in setting the time zone and anty location being reported in 'Find My Mac'
The problem was fixed by following advice itto reset accessibility in Terminal (taken from here):
tccutil reset Accessibility
Doing so fixed the precise location feature for setting the timezone and enabled the location of my computer to be determined in 'Find My Mac' in iCloud (and in 'Find My iPhone' app in iOS) instantly.