1. Check if the user has the appropriate device and permissions to join the call.
2. Verify that the user is logged in to the same account that has been invited to the call.
3. Make sure to use a supported device or browser.
4. Ensure that the audio, video, and microphone settings are selected in the device.
5. Reconfirm that the user has accepted the call invitation in the calendar event
6. If you are trying to join a call with more than four users, check if you are in participant mode.
7. If you are having issues joining the call, reach your IT team for specific advice.