I added this mod to the server midway and found that it caused the generated map to be very fragmented. I tried modifying the configuration file but couldn't solve the problem. What should I do to update the missing chunks, thanks

Hey, if you haven't done a full render of your worlds yet. That should fix it for you.
/map fullrender [world]

As mentioned above you need to run a full render. Chunks won't render on their own unless they have block changes while squaremap is installed.