If any case you encounter this issue, please verify the following:
1. Verify that the "Offline" user status is not manually set to Offline. You can check this by making them click their initials on the VSee address book and select Online.
2. Make sure that the VSee id that their using is the one you have added to your contact list. It might be possible that their logged in or using a different one.
After doing the steps above and the issue is still there, please report the issue to firstname.lastname@example.org