Can you try interrogating the button with the interrogation form drop-down set to "Select Element"? See if there is a hyperlink (A tag) under the button that you can interrogate instead. The PerformClick may work there.
Actually am not getting <A> tag when interrogating button in SelectElement mode only am able to see <Button>,<DIV> .Please help to solve ,even tried with hidden control also, but still performclick is not working for the button, where as it is working when I tested with Test Target Methods.
I suspect your issue is that the website doesn't know you've set the text in the search box and therefore the button is disabled. Try raising the OnChange or OnKeyUp events on the text box before you click the button. You may have to examine the HTML of the page to see which events are being triggered. Let me know if that doesn't work and I can try to get it to work here since your site seems to be public.
I tried raising the Onchange and Onkeyup event on the text box but still its not working. Kindly try it from your end and share the screenshot of the working automation. Site-URL : https://www.flipkart.com/
I was unable to resolve this with anything quick that I tried. It appears as though the site is using some JS that requires any changes be also propagated up to parent DIVs. You might want to open a SR to have this looked at with a member of support as this may require some time and effort to investigate.