Summary:
When you are updating the supervisor for users in Web TimeSheet using the CSV import feature available in integrations without the start date and the end date of the supervisor,  the following error is displayed when you hover the mouse pointer on the red icon with white X.
 
Setting the 'Supervisor Login Name' requires the Supervisor Start Date, Supervisor End Date field(s) to be set.
 
Hence to import supervisor information using the "CSV import" feature you have to mention the start date and the end date of supervisor.
 
Workaround:
If you want to update the supervisor name and do not want to specify the start date and the end date for the supervisor then contact Replicon Support and we will assist you import the data via our conventional import procedures which allows importing supervisor information without the need of a Start Date/End Date for the supervisor.