If you are using the Project app in Odoo, ensure that everyone who needs to log time on tasks is registered as an Employee in the system. Otherwise, they will not be able to log their time.
This is because timesheets in the system are linked to employees. Which means for a timesheet to be created, the system requires the user to be associated with an employee profile.
This setup can present challenges when working with external contractors who may not need to be internal users in your system. While there is an employee type called Contractor, it is currently not possible for an employee to be linked to a portal user. This means that if external contractors need to log time on projects, they must have an internal user account in the system.
Hopefully, Odoo will consider adding a dedicated Contractor user type in the future, which will extend the Portal user type, enabling these users to collaborate on projects and log time without requiring an internal user profile.