When you Log in, the message "This group cannot use Teachme Communication. Please contact your administrator." may appear.
Cause
Teachme Communication is not enabled for your Group.
Resolution
Please Contact your Group administrator. You will need to confirm the contract and activation status of Teachme Communication.
Related
Tell me about Log in and Logout
https://help.communication.teachme.jp/hc/en-us/articles/61437931024537