A validation error is received by a user while submitting a timesheet.
If accidentally a Validation rule is assigned to the users profile it will prevent the user from submitting the TimeSheet for Approval.
Log into Web TimeSheet as the administrator.
Edit the user profile.
Select the Advanced tab.
At the bottom of this page, the last option is Validation Rule.
Delete the validation rules by clicking the red x next to it.
Note: Once the validation rule is removed from the user profile the user will be able to submit the timesheet for approval.