A group of Microsoft Products and technologies used for sharing and managing content, knowledge, and applications.
Hi Tanner,
Based on your sharing, the error message List subaction 29 (addSPView) is invalid. Parameter name has an invalid value. means SharePoint generated an addSPView operation with a missing, unsupported, or otherwise invalid view name. Since the issue begins immediately after adding a Lists form, I suspect the metadata that the "From existing list" provisioning process is incorrectly treated as a conventional SharePoint view. That said, this could be a SharePoint Online service defect or unsupported interaction between Lists forms and list duplication.
For you to receive the best possible assistance in this case, I highly recommend contact your company's IT department and ask your administrator to create a support ticket through the Microsoft 365 admin center for further investigation. This route ensures you can contact a technical support engineer, who can perform a remote session to investigate the situation, verify the backend configurations, and run any necessary synchronization tools to resolve the problem. If the issue requires further attention, they can escalate it to a specialized team for deeper analysis.
- For detailed guidance on how to open a support ticket with Microsoft Support, please refer to: Get support - Microsoft 365 admin | Microsoft Learn
- In case you do not know who is your IT admin, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support
I hope this helps point you in the right direction. If you have any updates or additional questions, feel free to reply back and I'll do my best to assist further.
Hope you're able to get this resolved soon.