Symptoms

• Active Citrix ICA sessions become greyed-out or unresponsive after the endpoint workstation remains locked for approximately 30 minutes.

• Users are unable to interact with or recover the frozen session and must launch a brand-new session.

• Issue occurs on on-premise environments following an update to Citrix Workspace App Version 2511.

This behavior is tied to session reliability, EDT lossy transport settings, or unhandled exceptions introduced with the Connection Strength Indicator (CSI) feature in version 2511 triggering aggressive idle timeout drops during locked states.

Apply one or more of the following resolutions based on your deployment configuration:

Method 1: Disable Connection Strength Indicator (CSI) via GPO

The CSI feature added in version 2511 can misbehave during idle or locked workstation states.

1. Open the Local Group Policy Editor (gpedit.msc) or your domain GPO management console.

2. Navigate to Computer Configuration > Administrative Templates > Citrix Components > Citrix Workspace > User Experience.

3. Open Manage Connection Strength Indicator Notifications and set it to Disabled.

4. Alternatively, disable CSI notifications via StoreFront or Global App Configuration Service (GACS) session experience settings.

Method 2: Update Workspace App to the Latest Minor Release

Update affected endpoints from base version 2511 to version 2511.1 or later. Modern maintenance releases contain explicit fixes for unhandled exceptions (such as ntdll.dll faults) and session reliability grey-screen triggers.

Method 3: Tune EDT and Session Reliability Policies

If your environment uses EDT Lossy mode alongside older Virtual Delivery Agent (VDA) builds, adjust the transport settings in Citrix Studio:

1. Open Citrix Studio and navigate to Policies.

2. Locate and edit your HDX/Transport policies.

3. Temporarily disable or tune EDT Lossy transport mode or increase the Session Reliability Timeout thresholds to prevent premature drops during lock states.

Method 4: Roll Back to a Stable Release (Workaround)

If applying updates or GPO changes does not resolve the issue in your specific on-premise architecture, temporarily revert the client endpoints to a stable release baseline, such as Workspace App LTSR 2507.

Users running Citrix Workspace App version 2511 experience a greyed-out or frozen session after leaving their screens locked for extended periods (e.g., 30 minutes). This forces users to terminate the unresponsive session and launch a new one.