Hi iron_flower,
Do you try this with other account?
In my research, user accounts are required home in Skype for Business Online in Teams only mode.
Please make sure the account is home in Skype for Business Online.
For more details about Teams Only mode, please refer to:
https://docs.microsoft.com/en-us/microsoftteams/migration-interop-guidance-for-teams-with-skype
If it is no help, I suggest you
contact AudioCodes phone support for more details.
Best Regards,
Sharon Zhao
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