Hello @Pei_Shao
“parent object” of “Set Object Relations” wait for an object with “objectId” property. But you use the object with “comment” property.
“children” of “Set Object Relations” wait for a list with “objectId” string. But you use the object.
Logic for your case:
I don’t know if it’s appropriate, but I would advise you to use the id of user instead of username.
Regards,
Viktor