Dear RiverSlaney,
Thanks for using Microsoft products and posting in the community.
I understand that you can't save events to the New Outlook calendar. Thank you for your efforts and attempts.
Cause:
Recently, many users have reported the same issue. Based on their feedback, they have experienced issues when using non-Microsoft email accounts. When the third-party email (Gmail/POP/IMAP) is set as the main account for New Outlook, the calendar will trigger an issue where events cannot be added.
In this case, only the main account is unable to add a calendar, while other accounts in the app can be added normally.
Temporary plan:
Add an infrequently used email as the main account. The main account cannot add calendars, but the user can add another email they want to use normally.
The best thing is to add a Microsoft email as the main account (because this way the main account calendar is normal). Of course, we understand that not all users need to create a separate Microsoft account for this issue. So, the suggestion is to temporarily add another infrequently used email to New Outlook as the main account.
In addition, you mentioned that it can be used normally on other devices, so if you are willing, using other devices to use this feature can be a temporary solution.
Problem Progress:
We have gathered and submitted fixes for the issues. You can also provide feedback on this feature request directly from the new Outlook (Help --> Feedback --> Report a Problem).
Contact support and provide feedback in new Outlook for Windows - Microsoft Support
Thank you very much for your contribution. Sorry for any inconvenience caused to you.
I will share any updates with you if there is progress.
Best Regards,
Addie.C - MSFT | Microsoft Community Support Specialist