A project manager is unable to view the PTO of employees in Allocation and Forecasting. They are all included in the same group, but the project manager is still unable to view PTO.
You need to check the security permissions Allow access to allocation of all employees and Allow view all projects for the project manager. This can be found by going to Settings > Security Permissions and selecting the project manager's security profile. There under the Allocation and Forecasting section, you should find these permissions.