When you approve time, the system treats it as a signal that the entire pay period is finalized. To protect the integrity, it locks the period so no further changes can be made. Given that your employees are still in the middle of that same period, they’re being blocked from entering their second week.
To ensure that they’ll be able to track their time, you’ll need to unapprove their initial timesheets. Since you’re on a bi-weekly payroll, you can wait until the entire period ends.
If you have any other questions, feel free to let us know. We’re here to help.