The Modern UX is displaying a blank page (e.g.: white or gray background) where it is expected to see the Add Task button or the timesheet tasks for a specific timesheet and user.
The timesheet opens in the Classic UX URL (https://example.com/niku/nu#action:timeadmin.timesheetBrowserReturn).
There is an orphaned record in the database.
Run the following query in your Clarity database:
select * from prtimeentry where prtimesheetid = 5xxxxxx
(replace 5xxxxxx with the ID shown in the URL after timesheetId: https://example.com/pm/#/timesheets/timesheet?timesheetId=5012345&resourceId=5123456&timeperiodId=5234567)
This query should return the same entries shown in the timesheet in Classic UX. For example, if the timesheet is empty, it should return no rows (0). If these numbers do not match, please contact Broadcom Support for assistance.