Elm Language Server is not working

$ tree

├── README.md
├── elm-stuff
│   └── 0.19.1
│       ├── Main.elmi
│       ├── Main.elmo
│       ├── d.dat
│       ├── i.dat
│       ├── lock
│       └── o.dat
├── elm.json
└── src
    └── Main.elm

this is :LspInfo

Thus, even though elm.json exists, elm’s LSP does not work.
What settings should I make?