Event 1315 ASP.NET 4.0 "Membership credential verification failed" using LDAP Authentication in Win Server 2008 R2

Hello,

I have an VB application in IIS 7.5 Windows SQL Server 2008 R2 that authenticates users using AD. This has been working fine until recently. I keep seeing this messages in the Event Viewer. I then attempted to login myself and I get the application's exception that my username or password is incorrect when I know this is not true.

I've been searching online for any suggestions based on the message from the Event Viewer but no luck. I'm not implementing ASP membership roles. The identity for my application pool is the default one "ApplicationPoolIdentity" Integrated pipeline mode. Any help will be greatly appreciated.

Event code: 4006
Event message: Membership credential verification failed.
Event time: 2/6/2017 11:01:43 AM
Event time (UTC): 2/6/2017 5:01:43 PM
Event ID: 9afe66737e4d46f1a49230715d5943a8
Event sequence: 10
Event occurrence: 1
Event detail code: 0

Application information:
Application domain: /LM/W3SVC/1/ROOT/MyApplication 
Trust level: Full
Application Virtual Path: /MyApplication
Application Path: MyApplication path 
Machine name: ServerName

Process information:
Process ID: 6284
Process name: w3wp.exe
Account name: IIS APPPOOL\ASP.NET v4.0 Classic

Request information:
Request URL: http://hostname/MyApplication/Login.aspx
Request path: /MyApplication/Login.aspx
User host address: Server IP Address
User:
Is authenticated: False
Authentication Type:
Thread account name: ServerName\Administrator

Name to authenticate: username

Here is my Web.config file:

<?xml version="1.0" encoding="utf-8"?><!--
  For more information on how to configure your ASP.NET application, please visit
  http://go.microsoft.com/fwlink/?LinkId=169433
  --><configuration><connectionStrings><remove name="LocalSqlServer" /><add name="LocalSqlServer" connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=false"
      providerName="System.Data.SqlClient" /><add name="ConnString" connectionString="Data Source=Server IP Address;Initial Catalog=DB Name;Persist Security Info=True;User ID=sa;Password=*****;"
      providerName="System.Data.SqlClient" /></connectionStrings><system.web><compilation debug="true" explicit="true" strict="false" targetFramework="4.0" /><authentication mode="Forms"><forms loginUrl="Login.aspx" timeout="2880" /></authentication><identity impersonate="true" password="*****" userName="Administrator" /><sessionState timeout="5" /></system.web><system.webServer><modules runAllManagedModulesForAllRequests="true" /></system.webServer></configuration>