Hi @andaizhao. Thanks for asking about this. I replied to you in another channel already as well.
The issue is that this monorepo support is only in the Xenial build image and this site is still on Trusty. Changing to Xenial (in the site build settings in our the web UI) should be all that is required to get this working.
If there are other questions or that change doesn’t fix this issue, please let us know.