The location comes up as unknown because you have not set up the ipinfo OR google geolocate APIs which are used to get the geo-location for the IP addresses. Check your gophish.config file in your goreport directory
Gophish performs it’s own geolocation lookups with IP addresses and returns latitude and longitude. This works alright, but may fail and return coordinates of 0,0 or may return old information.
Goreport has two options that might be used to improve location results. The first, and recommended option, is the ipinfo.io API. API access is free as long as you make less than 1,000 queries per 24 hour period. That should not be too difficult for a phishing campaign.
If an ipinfo.io API key is added to the config file Goreport will automatically use ipinfo.io to gather current geolocation in formation for each unique IP address.