---
title: "Client Error Key not valid for use in specified state"
slug: "client-error-key-not-valid-for-use-in-specified-state"
updated: 2025-12-13T14:15:41Z
published: 2025-12-13T14:15:41Z
canonical: "support.appgate.com/client-error-key-not-valid-for-use-in-specified-state"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://support.appgate.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Client Error Key not valid for use in specified state

### **Log.log message**

**'Internal.Cryptography.CryptoThrowHelper+WindowsCryptographicException: Key not valid for use in specified state.**

## Resolution / Suggested Action

Uninstall the AppGate SDP Client, delete the certificate, and reinstall the Client, as detailed below.

#### **Uninstalling the AppGate SDP Client**

1. Press the **Windows+R** keys together, or type "run" in the Windows search field and press **Enter**.
2. Type "control panel" in the **Open:** field.
3. Click **OK** to launch the Windows Control Panel (below).
4. Click **Programs**.
5. Click **Programs and Features**.
6. Select the **AppGate SDP** client.![](https://cdn.us.document360.io/e7482ce5-acfa-4c3b-b76c-b6c32472644a/Images/Documentation/client-error-key-not-valid-for-use-in-specified-state-image-0hc8amck.png?sv=2026-02-06&spr=https&st=2026-10-26T23%3A58%3A21Z&se=2026-10-27T00%3A58%3A21Z&sr=c&sp=r&sig=7Gqefz9OcwSThSx4VgQzTja7vLdqMWrQ8FVQs7oGRN0%3D)
7. Click **Yes** to allow the program to make changes. An AppGate SDP Uninstall window appears:![](https://cdn.us.document360.io/e7482ce5-acfa-4c3b-b76c-b6c32472644a/Images/Documentation/client-error-key-not-valid-for-use-in-specified-state-image-rgdj9izh.png?sv=2026-02-06&spr=https&st=2026-10-26T23%3A58%3A21Z&se=2026-10-27T00%3A58%3A21Z&sr=c&sp=r&sig=7Gqefz9OcwSThSx4VgQzTja7vLdqMWrQ8FVQs7oGRN0%3D)
8. Click **Next** to uninstall the Client.

#### **Deleting the Defective Certificate**

1. Press the **Windows+R** keys together, or type "run" in the Windows search field and press **Enter**.
2. Type "certmgr.msc" in the **Open:** field.
3. Click **OK** to launch Microsoft Certificates (below). Use Microsoft Certificates to locate and select the defective Certificate. ![](https://cdn.us.document360.io/e7482ce5-acfa-4c3b-b76c-b6c32472644a/Images/Documentation/client-error-key-not-valid-for-use-in-specified-state-image-jwhy89g7.png?sv=2026-02-06&spr=https&st=2026-10-26T23%3A58%3A21Z&se=2026-10-27T00%3A58%3A21Z&sr=c&sp=r&sig=7Gqefz9OcwSThSx4VgQzTja7vLdqMWrQ8FVQs7oGRN0%3D)

4.Use Microsoft Certificates to locate and select the defective Certificate.

5. Right click the certificate, and select **Delete** from the resulting menu.

#### **Re-Installing the AppGate SDP Client**

Re-install the client as detailed at **Getting Started > Installing Clients** in your ***AppGate SDP Admin Guide*** (find the Admin guide for your AppGate SDP version [here](https://www.appgate.com/support/software-defined-perimeter-support)).