Calendar app crashing MS Teams webapp

Workaround 1: Ms Teams > top right "more options" menu > Toggle "New Calendar" off

Workaround 2: Use MS Outlook to access your calendar and join calls

Related observation: I also keep getting this banner, and apply restart has no effect:

Language changes detected (Deutsch). Please restart Teams to see the change. [Apply and restart] [X]

Since this forum is a public platform, I have modified your question to hide your personal privacy. For future posts, kindly avoid sharing personal or organizational information to protect your data.

Hello @Malte,  

Thank you for reaching out to the Q&A forum! 

I hope you can also understand that although your concern is technically outside the usual scope of my support responsibilities, I will still do my best to guide you in the right direction:

To support you better, please provide me more detail:

1.In addition to clearing the cache and logging in fresh, did you also try testing Teams Calendar in an Incognito/Private window?

2.I also noticed that your post is tagged under “Business.” Are you using a work (organizational) account, or a personal account such as Outlook.com or Hotmail.com? 

Besides that, after researching this issue, I could not find any official Microsoft article that documents this specific error. However, based on the error message you shared, it appears to be a client‑side issue, specifically related to the file: owa.hostedcalendar.xxxxxx.js 

This strongly suggests that the problem is caused by an internal JavaScript error, where a required module for initializing the Calendar is failing to load correctly. 

Because of this, I believe your case may require a deeper investigation from Microsoft’s advanced technical support team, as they have access to backend diagnostic tools and tenant‑level data.

If this is a work account, I highly recommend raising a support ticket with Microsoft’s higher‑level technical team as soon as possible.   

(If you are not the global admin, please kindly ask your IT Admin to do it for you)

• To create a Support ticket, you can go to: Microsoft 365 admin center                     
• When you click Help & Support in the bottom-left corner, a Support Assistance panel will appear.         
• In the text box, you can type: "request an agent to contact me via email or phone" and press Enter.         
• After that, please look at the bottom-left corner of the panel. You will see a blue link that says, "Contact Support"; you click on it.      

• You will then have two options: Support via phone or Support via email. You can choose Email. 

Please follow this article: Get support - Microsoft 365 admin | Microsoft Learn   

When the ticket is opened, a support engineer can start a remote session to investigate the issue, review the back-end settings, and optionally run a sync tool to resolve the issue.  

I apologize for redirecting you to the support team. As forum moderators, I have limited access to backend systems and cannot directly investigate device-level issues.       

I truly hope you’ll be assisted soon by our dedicated technical team. And if you receive any updates or insights, please feel free to reply here.       

Note: If this is a personal account, please reply so I can guide you to the appropriate support team. 

Looking forward to hearing from you! 

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