Setting up future meetings with participants using Teams calendar or Outlook integration
When you create a new meeting and add a participant, the Teams Meeting toggle remains off. If you manually click the toggle to turn it on, does it work?
In calendar settings > Events and invitations > please check if Add online meeting to all meeting is enabled. If it is turned off, when you add an attendee, the toggle will remain off.
Please check and let me know how it goes. If the issue persist, please let me know whether you are a normal user or IT admin of your company.