Using Classic Outlook on Windows for personal email, calendar, and contact management
Dear N Brenner,
Good day!
Thank you for posting to Microsoft Community. We are happy to assist you.
Before we proceed, I would require more information to assist you accurately.
May i know the version of the outlook? note that:
By default, Outlook 2016, Outlook 2019, and Outlook for Microsoft 365 use a new modern authentication stack. Even if the Internet calendar file that you are trying to open does not require authentication, Outlook broadcasts its ability to do modern authentication on the server that contains the calendar. Most server software responds to this broadcast by supporting modern authentication. However, some servers consider the broadcast to be an invalid client request. Therefore, they return a response that causes Outlook to cancel the attempt to add the calendar.
For example, server software that's running on Amazon Web Services (AWS) may consider the authentication broadcast to be invalid and refuse the connection.
Workaround
To work around this issue, use Outlook Web App (OWA). OWA doesn't have this authentication header behavior. Therefore, it will successfully open the Internet calendar that you want to add.
To use OWA to add the calendar, follow these steps:
- Sign in to OWA.
- Switch to the Calendar module.
- Select the Add calendar menu.
- Select the From internet option.
- Provide the URL and an optional calendar name.
- Select Save.
Reference: Cannot add an Internet calendar - Outlook | Microsoft Learn
- What is the type of account in outlook? Is it a POP, IMAP, or Exchange account?
2. Please try to see if import your Google Calendar to Outlook can resolve the issue.
Do this step for each Google Calendar you want to import to Outlook.
- In Outlook on your desktop (Outlook 2013 or Outlook 2016), go to your Calendar.
- Choose File > Open & Export > Import/Export.
- In the Import and Export Wizard, choose Import an iCalendar (.ics) or vCalendar file, and then choose Next.
- Browse to where you stored the extracted file, and choose the one that ends with gmail.com, and choose OK.
- Choose Import.
let see if you can see the google calendar. Reference: https://support.microsoft.com/en-us/office/import-google-calendar-to-outlook-098ed60c-936b-41fb-83d6-7e3786437330
3.Did you subscribe to a google calendar? Reference**:** https://support.microsoft.com/en-us/office/see-your-google-calendar-in-outlook-c1dab514-0ad4-4811-824a-7d02c5e77126****
The information is more important to find out the cause of your issue and provide the right troubleshooting.
Please get back to us with necessary information, we’ll be glad to assist you further.
Appreciate your patience and understanding and thank you for your time and cooperation.
Sincerely,
Eben Ezer Tres | Microsoft Community Moderator