Hi @Emmy
According to our research, there are a few possible causes and solutions that you can try:
- Check and update if the Microsoft Teams is the latest version.
- PSTN conferencing is not turned on for your account. You need to contact your IT admin to enable this feature for you.
- The correct licenses for PSTN conferencing are not purchased or applied. You need to check your subscription plan and make sure you have the necessary licenses for this feature.
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