If check-ins (legacy feature) are not working on your child's Chromebook, let's check their location settings and permissions.
On your child's Chromebook, select the time on the bottom right.
Double-check it's connected to Wi-Fi.
Then, select Settings.
In the "Google Play Store" section, select Google Play Store.
Select Manage Android preferences.
In the "Personal" section, turn Location on.
Then go back to Manage Android preferences.
Select the Bark for Chromebooks app, then select Permissions.
Then, turn Location on.
Re-open the Bark for Chromebooks app and tap Check In. It should now work!