It seems that the site requires location information and cannot cope with location blocking. Also, I get an error "Location information is unavailable."
Yes, it is location based, so it needs your location, or it can't do anything. Depending on your browser you should be able to click something like "allow location".
yes but what if my location is not determined correctly by the browser (eg when connected via a VPN with entry point in another city/country)? I must be able to specify my location manually.