We have added Fiscal Time Periods to enable the Timesheets to show in 2023, the fiscal time periods are active but not showing in the Modern UX on the Timesheet view.
Clarity 16.0.2 Time Management
Time reporting periods should be open for the required time period in 2023. i.e. Create time reporting periods (Classic PPM > Administration > Project Management > Time Reporting Periods). The time reporting period must have a status of open to enter time in the period.
For additional documentation information on creating Time Reporting Periods please visit : Configure Timesheet Reporting Periods