I wanted to use CCAvenue payment gateway on my store so I registered with CCAvenue and download OpenCart extension form their site. There were two options for this extension, first was for OpenCart version 2+ and other was for 1.5+. My store was on OpenCart 1.5.4 so I download second one and installed on my store.
After installation I configures all the information from my CCAvenue account and when I tried to place an order I was successfully redirected to CCAvenue payment page from my store but after payment I was redirect on a blank page of my store instead of payment successful message. I check in admin and found that payment status was update for the order so the issue was only correct message was not displayed to the customer.
When I contacted to BlueZeal team (extension developer) they said that I have older version of plugin that is why I am facing this error, but because I download this plugin through CCAvenue site so this was not the case with me. Upon my second request they replied with correct solution.
So the actual problem was that the files I download having wrong name. There was a catalog template file named CCAVEN~2.TPL which should be renamed to ccavenuepay_response.tpl. Please note that all the character should be lower case.
After renaming this file I tried payment again it worked like a charm.
So for all those having this issue just rename his file and you are done.