Microsoft Teams' Public Switched Telephone Network (PSTN) integration has fallen over.
The integration is a key part of Teams in the enterprise, and permits the use of phone calls with Microsoft's messaging platform. The afflicted service in this case appears to be Direct Routing.
Further investigation has determined that this issue could potentially affect any user attempting to make or receive PSTN calls via Direct Routing. More information is available in the admin center under TM289868.— Microsoft 365 Status (@MSFT365Status) October 7, 2021
Problems initially appeared to be confined to EU users, but Microsoft eventually admitted that pretty much any user could be affected. And goodness, they certainly seem to have been.
It appears that it's affecting the US phone numbers for Microsoft Teams as well. I have tried all of them, and it rings for a while then goes to a busy signal or disconnects.— Jamie Adamson (@JamesPokc) October 7, 2021
Despite the initial assurance from Microsoft, users from outside the EU began piping up and complaining of borkage. A glance at the notification in the Administration Center shows Microsoft looking into the issue, warning: "This issue may potentially affect any user routed through the affected infrastructure."
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Direct Routing allows Teams users to make and receive external phone calls on any device using Teams. It being down is most definitely a bad thing for users seeking to communicate outside of the Teams ecosystem. Skype for Business featured the Cloud Connector, which hooked up to a PSTN. However, the service was retired in July 2021 in favour of Direct Routing.
Which appears to having a bit of a moment.
The Register contacted Microsoft (not by phone, obviously) to find out what had befallen its service and will update should the company respond. ®