Integration of Gitlab and JIRA cloud for smart commits

We use JIRA cloud and Gitlab cloud in our organization.

I have been trying to get the development panel in JIRA for the smart commits to be displayed.
I have followed the steps in
But that didn’t solve my problem.Not able to view the commits/development panel on JIRA

At the step 2 of JIRA configuration, when I fill all the details required(client id, secret, user account etc), I get the error “This site cannot be reached” “The site has refused to connect”

Could you help me understand what is that I could be probably doing wrong?