Sprint field disabled for a few users in JIRA
Few users are not able to assign issues to sprint as Jira Agile sprint field drop down is disabled.
Those users are not given the Edit Issues & Schedule Issues permission from the Project Permissions page.
Grant those users Edit Issues & Schedule Issues permission from the Project Permissions page.
1. Log in as a JIRA Administrator.
2. From the top navigation bar, click on Projects -> choose the affected project.
3. Click on the Administration tab -> Select Permissions of the left pane.
4. At the Default Permission Scheme page, click on Actions -> Edit Permission
5. Locate Edit Issues & Schedule Issues permission and make sure the user in included in the appropriate group already associated to this permission by checking the groups page.
6. If the user is not, click on Add and associate the user directly to those permissions.