Element Found in Developer Tools But no in CSS & Xpath Checker

Root cause found for thread:-
http://forum.katalon.com/discussion/comment/22512#Comment_22512

some where in Katalon KB articles recommended CSS & Xpath Checker hence I installed that in chrome browser, strange thing is my xpath //input[@id=‘firstname’] is not detected by CSS & Xpath Checker but the same is being detected by developer tools, because of this I suspect katalon unable to detect text box element in iframe

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