To be able to register hours, a number of conditions must be met:
A project must have been created.
The project must have a service.
'Register hours' must be enabled, and the registration must fall within the start and end date.
An hour type must be added to the service.
If you have met the above conditions, you can also check whether you have entered a start and/or end date in the time registration (on the service). If so, you can only register hours between these dates.
Additionally, you can add a team for each project. By default, all employees can log hours. However, once you have assembled a project team (based on teams or individual employees), only the employees in the project team are authorized to register hours on that project.
Finally, the employee themselves must have an active schedule. If you want to register hours on a specific date, that date must fall in the employee's schedule.
If all the aforementioned conditions are met, then you can register hours!