Occasional Visitor

We just started using Teams at our school, and all of the older students have been added to the system. I have noticed that when the student is shown as offline, I am not able to send a chat message, and the screen at the bottom says, "Administrator has disabled chat for this user."  I have triple checked the permissions, and they have chat permissions.  


And it's not consistent with all users.  

Help!  How do I enable chat, even if they are offline?