Create a WorkFlow in Oracle Sales Cloud

Hi,

I have written a Object workflow on Partner to update a field when

 if(isAttributeChanged('LivelloAppoggio_c'))

 {

   return true;

 }

where,

LivelloAppoggio_c = Choice List (fixed)

this is the condition for the workflow to get fired on Update. The workflow does not trigger the field Livello_c when I change the value of LivelloAppoggio_c and save the record. I tested also other condition but the wf doesn't work .Why the conditions doesn't work? I need to work with wf because in the future i will use it in an asynchronous process based on a date field.

Can you kindly help me?