Set a value from one text field from one content type to another text field in another content type using set data value in rules
Here is example


Content type Article: field_product - Product reference
Content type Basic page: field_product2 - Product reference


Article creation triggers next actions:

{ "rules_on_article_create" : {
    "LABEL" : "On Article create",
    "PLUGIN" : "reaction rule",
    "OWNER" : "rules",
    "REQUIRES" : [ "rules" ],
    "ON" : { "node_insert--article" : { "bundle" : "article" } },
    "DO" : [
      { "entity_create" : {
          "USING" : {
            "type" : "node",
            "param_type" : "page",
            "param_title" : [ "node:title" ],
            "param_author" : [ "node:author" ]
          },
          "PROVIDE" : { "entity_created" : { "entity_created" : "Created entity" } }
        }
      },
      { "data_set" : {
          "data" : [ "entity-created:field-product2" ],
          "value" : [ "node:field-product" ]
        }
      }
    ]
  }
}


I think you r trying to operate with non existing object. When you r creating node of type B there is no link to any another node in rules.