Why my shell script doesn't work in Alfred 2 Workflow

Why my shell script doesn't work in Alfred 2 Workflow

I wrote a script like this,
#!/bin/sh
HEXO=/Users/cinvro/nvm/v0.10.15/bin/hexo
cd ~/Work/hexo/cinvro.com/
$HEXO generate
it works when I execute it in my terminal,but it doesn't work when I put
it in a Alfred2 Workflow. Alfred will not print anything when executing
this workflow, and the script seems not been run.
hexo here is a node.js program.