MS Teams suddenly fails to save Teams events

I noticed that you posted your question in English, so I’ve replied in English as well. If you’d prefer to continue the conversation in another language, please feel free to let me know and I’ll be happy to adjust.

Dear @Petr Brož,

Welcome to Microsoft Q&A. 

Thank you very much for the clear and detailed description, I really appreciate that you’ve already tested this across different environments (desktop app, browser, and even an anonymous window) and confirmed that it works correctly for your coworker. That information is extremely helpful and rules out most client‑side or tenant‑wide issues.

Based on what you’ve shared, this behavior strongly points to an account‑specific backend issue, which can occasionally occur with Microsoft Teams Essentials since it uses a lightweight calendar service rather than Exchange Online. When the calendar service or event provisioning for a specific user becomes inconsistent, Teams may fail to save meetings with a generic message like “Event failed to save.”

At this stage, there isn’t anything further you can troubleshoot locally. Because this involves calendar and identity services that operate on the Microsoft backend, the next necessary step is to contact Microsoft Support so they can review and repair the calendar provisioning for your account.

I sincerely recommend you try to create a support ticket from Microsoft 365 Admin Center>Support>Help & Support.

The support team over there has higher permission than us to investigate the issue from background, they have more resource and correct escalation channel in handling this kind of issues. This would be a more efficient way in handling the case for you.  

For reference:  Get support | Microsoft Docs      

You’ve already done the right checks, and your findings significantly narrow the scope of the issue.

I hope this information helps point you in the right direction. If you need further assistance, please don’t hesitate to reach out again. I’ll do my best to support you however I can.  

Warm regards, 

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