Is TestComplete compatible with FireFox ?
What version of TestComplete are you using? Currently, TestComplete 12.50 supports up through FireFox 61 as per https://support.smartbear.com/downloads/testcomplete/firefox-patches/.
Likewise, TestComplete 12.50 supports Chrome 67 out of the box... but there is a requirement of having the Chrome extension installed in the browser. If the extension isn't installed, you won't be able to recognize objects in Chrome.
Finally we resolve this . Somehow we miss the following setting in firefox
we changed it to false. and it work now.