Why would two users have different levels of visibility to Jira tickets and comments?
User profile setups can have some level of impact on the ability to see certain Jira issues and comments. It is necessary to ensure authorized users have all the JCFS classes added correctly.
Please follow the steps at the documentation Create Jira issues and associate buttons are visible to Jira admins only.
We have clearly highlighted how to add these apex classes to the impacted user profile. This will enable the user to see all Jira issues and comments.