Error on project exporting

I was trying to export any projects from an older version Gitlab server (v11.1.1).
The steps are straight forward, based on the Gitlab instructions.
Settings > Export Project, then press the button of ‘Export Project’.
Then I received an email notice with the error (see following),
Project my-test-2 couldn’t be exported.

The errors we encountered were:

  • No such file or directory - tar

It looks like the command was not able to locate the right tar.
Anything in the configuration needs to modified?
Thanks for help!