...
To track their time, you must grant users the Work On Issues permission in their project. To verify your project permissions for time tracking:
Select
Settings > Issues.
Click Permission schemes.
Next to the permission scheme you want to configure, click Permissions.
In the Time tracking permissions section, go to the Work On Issues permission and click Edit.
Select the users, groups or project roles that need to log work on issues.
Click Grant.
...
Enabling time tracking for Jira Server/Data Center
Choose
> Click on Issues.
Select Issue Features > Time Tracking to open the Time Tracking page.
Click the 'Activate' button to turn time tracking ON.
...