Issue Summary

Prerequisite: the user's domain has been added to the approved domains list, granting access to JSM as a customer. 

If a customer account (Atlassian Account) is removed from the JSM customer access group, trying to access a portal using the same account results in an error indicating that the user doesn't have access. 

The access is not entirely blocked, after logging out, waiting for an undefined amount of time, and clearing the browser cache/cookies, it eventually works. 

Steps to Reproduce

Setup:

1. In /jira/settings/products/servicedesk/customer-access, enable the usage of approved domains:
   
2. In the JSM project, set /jira/servicedesk/projects/<YOUR_PROJECT>/settings/customer-permissions as Restricted:
3. Have the user's domain added to the approved domains list, granting customer access to JSM.

Reproducing the issue: 

1. Remove the user from the customer product access group. 
2. Try to access the JSM project channel.

Expected Results

The user should automatically receive access to JSM as a customer. 

Actual Results

1. The message “Joining Jira. Hang on just a sec...” will be displayed. 
2. Followed by the error: 

No Access
You don't have permission to view this portal.

It's worth mentioning that, right after the initial message “Joining Jira. Hang on just a sec...” the user account is already part of the default access group set for customer access in JSM.

In the developer console, we can see a 403 error in the endpoint: 

https://<SITE_NAME>.atlassian.net/rest/servicedesk/1/customer/models 

Response: 

{
    "status": 403,
    "reasonKey": "com.atlassian.pocketknife.api.commons.error.AnError",
    "user": {
...
},
    "errorMessages": [
        "You don't have permission to view this portal."
    ],
    "errorLogoClass": "default-error",
    "nextActionUrl": "/servicedesk/customer/portals",
    "nextActionDisplayText": "View other portals"
} 

Workaround

1. Completely log out from the Atlassian Account at https://id.atlassian.com/logout
2. Wait for a minimum of 10 seconds, and log in again.
3. If the error is still happening, reload the page multiple times by pressing F5 or force a “hard” refresh:
   1. Windows: Ctrl + F5 
   2. Mac: Command + Shift + R
4. Repeat this several times if necessary. 
5. It might be necessary to clear the browser cache + cookies. 

Other notes: 

It seems like this behavior could have some relation to the bug reported in the Confluence project where the behavior happens only when JSM is used along Confluence: CONFCLOUD-74283