Today, i faced an autocomplete problem for all user picker fields in jira cloud version .
User picker autocomplete field which includes all of issue types doesn't work ! 
I configured nothing about that.
I read that solution
"For Issues with Global Permissions
Make sure that the logged in user has allow browse user permission for whatever groups they are in - especially in the jira-users group.
To Allow the permission, do the following:
- Login to the JIRA application as the Admin.
- Go to JIRA Administration > System > Security: Global Permissions
- Set the permission for Browse User permission to allow jira-users group."
,checked permission scheme and assignable user permission and there's nothing wrong about permissions. Any logged in user can assign anyone but writing full user name ,such as : duygu.akdenizso autocomplete doesn't work. Please can you help me ?
Is this a global problem or something like that? Im using Jira cloud, Jira Service Desk Application 3.3.0-OD