Open the Bark Kids app and/or Guard Dog app on their device.
If prompted, allow the VPN. Otherwise, the VPN will reconnect on its own.
Wait a few minutes and/or restart the device.
Screen time protection should now have resumed!
Pro Tips
Keep an eye on the protection status under your parent app (child's profile > Devices).
Spot-check the phone for any third-party VPN apps.
Consider enabling App Approval to prevent your child from installing third-party VPN apps.