Siri unable to determine my location despite location services enabled
Signing into iCloud and turning on both Bluetooth and Wi-Fi ensures that your Mac has the best chance of finding its location.   I believe that if you sign into iOS devices that happen to have GPS or location services working, your Mac might be smart enough to figure out where it is based on sharing the same Internet connection in proximity, but I am not sure. 

The primary way that location is determined as if Apple knows the IP address you are reaching so be sure you turn off all VPNs and get on as open a network is you can initially. The second way is trilateralization from known WiFi access points that your WiFi can see. You don’t have to join those networks, but you need a viable network connection back to Apple.