I think this is related: #411.

I am using nix to install typescript which gives me the binary tsserver, which is in my path. However, when starting my lsp server, it gives the error message:

Request initialize failed with message: Could not find a valid tsserver executable in the workspace or in the $PATH. Please ensure that the "typescript" dependency is installed in either location. Exiting.

The solution is to use what one discussed in the issue linked by providing a explicit tsserver path. However this still means that the error message is misleading. Seems like the error is from finding a bundle version here: https://github.com/typescript-language-server/typescript-language-server/blob/master/src/lsp-server.ts#L180 which doesn't seem to look into $PATH.