Hi! I am using Houdini 16.5.268 and HtoA 2.2.0. I tried to import the lighting ass file by arnold_procedural in Houdini, but it didn't show up in the viewport. Also I tried to render it, but it came out with Error that showing “Error Command Exit Code: 1”.

The ass file was working fine in Maya, and the Arnold render was working ok without Arnold_procedural node.

Am i doning something wrong? or there are other way to import lighting in HtoA?

make sure you are using same versions of Arnold in both apps, then make sure you are pointing arnold rop to mtoa shaders.
https://support.solidangle.com/display/AFHUG/Sharing+.ass+Files+Between+Plugins [support.solidangle.com]