URGENT PLEASE. Remote event Reciever app hosted inside Azure is showing this error “[SecurityTokenSignatureKeyNotFoundException: IDX10501: Signature validation failed”

Question

I have a remote event receiver deployed inside Azure, and it is working well for 2 years. but yesterday i noted that the RER is not longer working !! now i went to site content >> click on the App , where i got this error instead of getting the web title:-

here is the code for the default.aspx page:-

protected void Page_Load(object sender, EventArgs e)  
        {  
            // The following code gets the client context and Title property by using TokenHelper.  
            // To access other properties, the app may need to request permissions on the host web.  
            var spContext = SharePointContextProvider.Current.GetSharePointContext(Context);  
  
            using (var clientContext = spContext.CreateUserClientContextForSPHost())  
            {  
                clientContext.Load(clientContext.Web, web => web.Title);  
                clientContext.ExecuteQuery();  
                Response.Write(clientContext.Web.Title);  
            }  
        }  

Answer 1

Please check if the client secret has expired, if yes, please update the client secret according to this document:https://learn.microsoft.com/en-us/sharepoint/dev/sp-add-ins/replace-an-expiring-client-secret-in-a-sharepoint-add-in

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