That’s difficult to troubleshoot, but if you’re inside then I’m guessing there’s either no location by GPS, or it doesn’t match the location added to trusted places (due to no accurate location being available either when unlocking or when adding the trusted location in the first place). There are reports that the FP2 switches wifi off when the phone has been in stand-by for 10 minutes - this may be making the problem worse as for a quick location fix Wifi is stated to work best (probably because accesspoint names are used to help determine location) and there is at least one report of smart lock forgetting where it is when wifi disconnects (here).
The only thing that I can think of that may help is to double check whether your trusted place is set-up correctly.