Please do as follows to resolve the server error in your eportal:
Initialise Calendar
Go to the Core module.
Click Setup and select Initialise New Year Setup.
Click Step 1 Calendar.
Select the current year and select all the calendars, and click Confirm.
Global Recalculate
Go to the Leave module.
Click Process Leave.
Click Global Recalculate.
Enable all leave.
Click Recalculate and click Yes
Update in Eportal
Log in to eportal as admin.
Click Settings and click Eleave Settings.
Click Configuration and click Copy all leave types.
Click Confirm.
Start and Stop IIS
Go to the eportal server.
Go to the IIS Manager.
Click Application Pools and select ePortal or ePortal V2
Click Stop and Start services
If the above steps do not help, try restarting the eportal server.