Troubleshoot SharePoint Security Token Service and Certificate Errors
Question details
Users are unable to access a SharePoint application, encountering NullReferenceException, missing certificate warnings, and STS activation errors.
- Product
- Microsoft SharePoint
- Device & OS
- not provided
- Scenario
- Opening SharePoint sites via browser shortcuts or by selecting 'Browse Website' in the SharePoint admin center.
- Observed behavior
- The SharePoint site fails to load for all users, returning Security Token Service (STS) activation errors and missing certificate messages.
Ensure you have SharePoint Farm Administrator privileges or access to the on-premises SharePoint IT support team, as resolving STS and certificate issues requires backend server access.
Investigate On-Premises Certificates and STS Service
Identify and replace expired local Farm certificates and ensure the Security Token Service application pool is running properly.
The presence of missing certificate warnings alongside STS activation failures strongly indicates that the on-premises SharePoint environment has an expired or improperly bound STS certificate.
Because these are infrastructure-level components, end-users cannot resolve them directly and must escalate the ticket to a Farm Administrator.
Contact your internal IT department or SharePoint administrator, noting that the error involves the Security Token Service and local certificates.
Log in to the SharePoint Central Administration server, open IIS Manager, and check if the SecurityTokenServiceApplicationPool is started.
Open the SharePoint Management Shell and run 'Get-SPSecurityTokenServiceConfig' and check local certificate stores to verify if the primary STS certificate has expired.
Test Alternative Access Methods
Rule out localized browser cache issues or broken shortcuts by accessing the SharePoint site through standard Microsoft 365 navigation routes.
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Frequently Asked Questions
What is the SharePoint Security Token Service (STS)?
The Security Token Service is a core SharePoint web service that issues, manages, and validates security tokens for user authentication across the SharePoint farm and federated applications.
Why do browser shortcuts suddenly stop working for SharePoint?
Shortcuts may point to specific session URLs or outdated authentication nodes. If backend configurations change or an authentication certificate expires, those exact shortcut links will fail to process the login request.
What causes a NullReferenceException in SharePoint?
This exception generally occurs when a custom web part, service, or background process tries to use an object that hasn't been instantiated. In this context, it happens because the STS failed to load due to a missing certificate.
Can end-users fix SharePoint Security Token Service errors?
No, STS and local farm certificate errors require SharePoint Farm Administrator privileges. End-users must report the specific error messages to their IT support team for resolution.
