GNSS Receiver not working

Hello. I purchased the Gravity: GNSS GPS BeiDou Receiver Module and tried the sample code, but the numbers displayed in Serial, such as latitude, longitude and number of satellites, are all zero and never change. The LED on the board also glows green when I put it outdoors, so I don't think it is a complete failure, but is there anything I can try? The code is directly from getGNSS.ino. I am Japanese and am writing this using a translation site. Sorry if there are any strange English words.