> Use Xpath and Css selectors checkbox is also selected
If you are talking about 'Use XPath and CSS selectors for web objects' project properties option, then .FindElement() method must be used instead of .FindChildByXPath().
> FindElement also doesn't work. Not sure what is the reason
Can you post a screenshot of the code and log?
> if I uncheck the 'Use Xpath and css selectors' property , will FindChildByXpath work?
Yes, it should, but this will disable cross-platform mode and switch back to default local one. (So you will not be able to execute your tests in CrossBrowserTesting and other cloud environments.)
Another possible reason is that page was not navigated to.
I believe I understood the issue here,
the same methods FindElement and FindChildByXPath works for other web pages in the same URL.
I doesn't work only in the initial page I think which might be due to security issue.
Can someone help me with this?
Yes, correct, this is security issue with Chrome (https://community.smartbear.com/t5/TestComplete-Functional-Web/Testcomplete-Firefox/m-p/215982/highl...) and I think that you will need to add your tested site to the allowed exceptions list.
I have tried this