Microsoft 365 Error Codes

How to Fix Microsoft Project Web App Errors 23000 and 26005

Guest Writer Oct 10, 2026 869 views

Question details

Users encounter error codes 23000 and 26005 when attempting to save and publish projects or change resource allocations in Microsoft Project Web App.

How to Fix Microsoft Project Web App Errors 23000 and 26005

Product: Microsoft Project Web App
Device & OS: not provided
Scenario: Saving and publishing tasks with assigned resources or modifying resource allocation percentages.
Observed behavior: The web application displays error code 23000 or 26005 and fails to successfully save or publish the task updates.

Before you start

Ensure you have a stable internet connection and verify with your project manager that your account holds the correct permissions to save and publish changes within the specific project.

Solution 1Recommended

Perform Basic Browser and Permission Checks

Clear local browser data and verify your user permissions before escalating the issue, as local caching issues can sometimes block synchronization.

In many web-based applications, outdated cache files or broken cookies can interrupt the communication between your browser and the server. Clearing these can quickly resolve superficial connectivity issues.

Check network connectivity

Verify that your internet connection is active and stable. Try opening other Microsoft 365 web applications to ensure you are properly connected to the service.

Clear browser cache and cookies

Navigate to your web browser's settings menu. Under the privacy or history section, select the option to clear browsing data, ensuring that both 'Cookies' and 'Cached images and files' are selected.

Verify user permissions

Confirm that your account has the specific authorization to save and publish tasks for the current project. You may need to ask the project owner to review your access level in the Project Web App settings.

Perform Basic Browser and Permission Checks

Restart Your Browser: After clearing your cache and cookies, completely close and reopen your browser before logging back into Microsoft Project Web App.

Solution 2

Contact Your Microsoft 365 Administrator for Backend Support

Because errors 23000 and 26005 often affect multiple users simultaneously, resolving them typically requires a backend investigation by Microsoft.

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Frequently Asked Questions

What does Error 23000 mean in Microsoft Project Web App?

Error 23000 typically indicates a server-side failure to save or publish project data. It is frequently triggered by backend synchronization issues when modifying resource allocation percentages or assigning resources to tasks.

Can clearing my browser cache actually fix Error 26005?

Yes, in some cases, corrupted browser cookies or a stale cache can interfere with the web application's ability to communicate properly with Microsoft 365 servers. Clearing this data forces a fresh connection.

Why do I need my Microsoft 365 administrator to fix this issue?

When errors 23000 and 26005 affect multiple users simultaneously, it strongly points to a server-side or tenant-level disruption. Only authorized administrators have the privileges required to open a backend investigation ticket directly with Microsoft Support.

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