'iframe:iframe' Doesn't work... Please help

I really really appreciate your patient and willingness to help me to start with.

I've used this tool multiple times with paid membership, I get used to how to paginate and scrape comments in a wrapper. But this time, Iframe gives a headache.

The whole comment component is in an Iframe, say if I want to get user name in the comments area, I tried iframe:iframe span.author but data return 'null' to me.

Did I miss something to make this work? Or is there any other little trick I can apply? Ultimately I want to scrape multiple pages of reviews(comments).

Again, thanks for clicking in and see my question!

Url: https://www.caradvice.com.au/750698/2019-bmw-330i-review/

Sitemap:
{"_id":"bmw3s","startUrl":["https://www.caradvice.com.au/bmw/3-series/reviews/"],"selectors":[{"id":"pagination-cars","type":"SelectorLink","parentSelectors":["_root","pagination-cars"],"selector":".col-xs-10 li","multiple":true,"delay":0},{"id":"article-title","type":"SelectorLink","parentSelectors":["_root","pagination-cars"],"selector":"div.recent-review-details h3 a","multiple":true,"delay":0},{"id":"features-wrapper","type":"SelectorElement","parentSelectors":["article-title"],"selector":"div.feature-ratings3-on","multiple":false,"delay":0},{"id":"car_specs_rating_overall","type":"SelectorElementAttribute","parentSelectors":["features-wrapper"],"selector":"div.lv-Rating","multiple":false,"extractAttribute":"data-ca-rating","delay":0},{"id":"car_performance_economy","type":"SelectorText","parentSelectors":["features-wrapper"],"selector":"div:nth-of-type(1) .u-container div.lv-Rating-value","multiple":false,"regex":"","delay":0},{"id":"car_cabinspace_comfort","type":"SelectorText","parentSelectors":["features-wrapper"],"selector":"div.lv-Rating:nth-of-type(2) div.lv-Rating-value","multiple":false,"regex":"","delay":0},{"id":"car_technology_connectivity","type":"SelectorText","parentSelectors":["features-wrapper"],"selector":"div.lv-Rating:nth-of-type(3) div.lv-Rating-value","multiple":false,"regex":"","delay":0},{"id":"car_price_features","type":"SelectorText","parentSelectors":["features-wrapper"],"selector":"div.lv-Rating:nth-of-type(4) div.lv-Rating-value","multiple":false,"regex":"","delay":0},{"id":"car_ride_handling","type":"SelectorText","parentSelectors":["features-wrapper"],"selector":"div.lv-Rating:nth-of-type(5) div.lv-Rating-value","multiple":false,"regex":"","delay":0},{"id":"iframe","type":"SelectorElement","parentSelectors":["article-title"],"selector":"iframe","multiple":false,"delay":0},{"id":"user_name","type":"SelectorText","parentSelectors":["iframe"],"selector":"iframe:iframe span.author","multiple":false,"regex":"","delay":0}]}

This one is tricky 'cos there's actually more than one iframe. The alternative is to just grab the source url from the iframe, then scrape that page separately.

{"_id":"caradvice-disqus","startUrl":["https://www.caradvice.com.au/750698/2019-bmw-330i-review/"],"selectors":[{"id":"disqus","type":"SelectorElementAttribute","parentSelectors":["_root"],"selector":"iframe[title=\"Disqus\"]","multiple":false,"extractAttribute":"src","delay":0}]}

The Disqus urls looks like this:
https://disqus.com/embed/comments/?base=default&f=caradvice&t_i=750698%20https%3A%2F%2Fwww.caradvice.com.au%2F%3Fp%3D750698&t_u=https%3A%2F%2Fwww.caradvice.com.au%2F750698%2F2019-bmw-330i-review%2F&t_e=2019%20BMW%20330i%20review&t_d=2019%20BMW%20330i%20review&t_t=2019%20BMW%20330i%20review&s_o=default&l=#version=b01df3a75e0d62888faea7d1827ec12d