How to Fix Project Online Site Stuck in Read-Only Mode
Question details
Users are unable to edit project schedules because the Project Online environment is completely locked in read-only mode.
- Product
- Microsoft Project Online
- Device & OS
- not provided
- Scenario
- Attempting to edit, update, or manage project schedules and tasks within a Project Online organization site.
- Observed behavior
- The site displays a persistent read-only error preventing any schedule modifications, affecting all users simultaneously even when storage and licensing seem adequate.
Ensure you have administrator privileges in the Microsoft 365 admin center, as troubleshooting this issue requires access to user license assignments and site quota metrics.
Verify Project Licenses and Storage Quotas
Use this method to rule out the most common causes of read-only restrictions: expired user licenses and maxed-out site storage limits.
Project Online requires active Professional or Premium licenses for users to edit schedules. Additionally, if your Project Web App (PWA) site exceeds its allocated SharePoint storage limit, the entire site defaults to read-only mode to prevent data corruption.
Log in to the Microsoft 365 admin center. Navigate to 'Users' > 'Active users' from the left menu. Select an affected user and click on the 'Licenses and apps' tab to ensure they have an active 'Project Online Professional' or 'Project Online Premium' license assigned.
Go to your Project Web App (PWA) site. Click the gear icon in the top right to open 'Site Settings'. Under 'Site Collection Administration', click 'Storage Metrics' to verify that your site has not reached or exceeded its storage limit.
Contact Microsoft Support for Backend Diagnosis
Use this solution if licenses are actively assigned, storage is sufficient, and the read-only error impacts all users globally.
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Frequently Asked Questions
Why did my Project Online site suddenly switch to read-only mode?
Sites typically enter read-only mode when the Project Web App storage quota is exceeded, when user subscriptions expire, or during a temporary service-side outage on Microsoft's backend.
How can I check if my Project Web App quota is full?
As a site administrator, navigate to 'Site Settings' in your PWA environment and select 'Storage Metrics' under Site Collection Administration. This page displays exactly how much of your allocated space is currently being consumed.
What should I do if my licenses and storage are fine but no one can edit?
If the issue impacts all users universally despite sufficient licenses and available storage, the problem is likely a service environment issue. You must contact your Microsoft 365 administrator to open an official support ticket with Microsoft.
Can a single user be stuck in read-only mode while others can edit schedules?
Yes. If only a single user is experiencing the issue, it is almost certainly a missing or expired 'Project Online Professional' or 'Premium' license for that specific account, rather than a site-wide problem.
