Microsoft is working to resolve a known issue that causes delays or blocks some users from opening the Microsoft Teams desktop client on Windows systems.
The company acknowledged this known issue (tracked as TM1466820) at 16:45 EDT on Thursday and advised affected customers to work around it by using the web or mobile platforms.
"Specifically, when first opening Microsoft Teams on Windows devices, some users may be initially unable to load the client or may encounter loading delays of up to two minutes," Microsoft said in an incident report seen by BleepingComputer.
"While we're focused on remediation, affected users may be able to avoid impact by utilizing Microsoft Teams on the web or alternative Teams access methods such as the Teams mobile app."
Microsoft is still analyzing service logs and telemetry data and has also reached out to some affected users to identify the root cause and determine mitigation options.
At the same time, it's investigating an issue preventing Mac users from joining Teams calls and meetings, tracked as TM1466659 and confirmed on Sunday at 08:32 EDT.
While Microsoft initially blamed a code change for causing the Teams call and meeting service infrastructure to fail to process some requests, the company is reassessing the root cause after further review found that this may not be the cause of the impact.
"Users may be unable to join calls or meetings in Microsoft Teams for Mac," it said. "We're reassessing our root cause understanding and reviewing service logs to isolate the source of impact, so that we can determine our next steps regarding impact remediation."
In April, Microsoft resolved another known issue that blocked some Microsoft Teams Free users from chatting and calling others.
On Tuesday, it also confirmed a bug causing crashes and launch failures for Microsoft Teams and New Outlook users after installing Windows security updates released since the August 2026 Patch Tuesday.
Earlier today, Microsoft notified customers that an ongoing Exchange Online issue affecting multiple mailboxes and triggering " Server busy" errors is delaying email sent to and received from external domains.
This is a developing story ...
Once attackers have valid credentials, only 37% of their actions are blocked
Overall prevention scores can hide what happens after initial access. Once attackers are using valid credentials, prevention drops sharply.
The Blue Report 2026 measures defenses technique by technique across 338 million simulations run in customer production environments.
Get the report