Unable to activate the '@' mention within JIRA fields

[Om]

@Mentions user feature is not working in my JIRA account but it is working fine for my colleagues. http://prntscr.com/m4unl9
Even I'm receiving emails when they mentions me: http://prntscr.com/m4uiq1

I tried to find online solutions, I found following articles but I didn't find any options mentioned here..
https://confluence.atlassian.com/jirakb/mentions-and-autocomplete-are-not-working-in-jira-cloud-779160727.html
https://confluence.atlassian.com/jirakb/mentions-are-not-working-in-jira-applications-289277743.html

Where I can find Gear Icon, System, Global Permissions etc.?

[Danny Coleman]

As mentioned in the articles you linked, you'll need the "Browse Users" global permission to be able see an autocomplete list of users that you can mention.

If you're not an admin, your Jira admin will need to change these permissions for you. Instructions on how to update these permissions can be found here:

https://confluence.atlassian.com/adminjiraserver073/managing-global-permissions-861253290.html

[Om]

Thanks @Danny Coleman

We have checked that My and my colleagues' access is 100% identical!
And we also tried by creating new account for me.. but same issue with new account.

Any other solution?