Gitlab for Jira

Hi there,

I am new on integrating Gitlab to Jira.
When I tried to connect JIRA to Gitlab through DVCS account, I got an error “Error obtaining access token. Cannot access https://<MY_HOST> from Jira.”

The environment of mine is Jira Cloud (standard version) and self-hosted Gitlab with self-signed certificate.

The steps I followed from the official documents of Jira and Gitlab are shown as below:

  1. Create an user - UserJIRA on Jira with site-admin permission
  2. Create an user - UserGitlab on Gitlab with admin permission
  3. On Jira, use the UserJIRA to create a personal API token
  4. On Gitlab, use UserGitlab to enable the integration of JIRA with the API token generated in step 3
  5. On Gitlab, Add a new application in a Group Settings
  6. On Jira, create a DVCS account using the application ID and secret generated from step 5 as the Client ID and Client secret.
  7. On Jira, click “Add” on browser would redirect to Gitlab
  8. On Gitlab, click “Authorize” in the same browser where is just redirected from Jira would return the page to Jira
  9. Receive the error message: Error obtaining access token. Cannot access https://<MY_HOST> from Jira.

Currently, I only have self-signed certificate for my self-managed Gitlab server.
Is this the reason of failing to integrate Gitlab to Jira?
Or what I missed for configuring?

Does anyone know what the problem is?
Or, how to debug for this?

Thanks for any help…