OWA (and whole Default IIS Site) give "HTTP Error 500.19 - Internal Server Error" after GPO dcgpofix

I recently had a big issue caused by a mistake of mine in the GPO. I ended up manually deleting the faulty GPO file and then running the "dcgpofix" command on the Default Domain Controllers Policy on a working domain controller. That allowed me to then log in and the AD network and policies now work.

What doesn't, is my Exchange 2010 installation. It now, since the "dcgpofix" command was done, the OWA, and the whole Default Site give a 500 Internal Server Error. It is the following:

Server Error in Application "DEFAULT WEB SITE" Internet Information Services 7.5
Error Summary
HTTP Error 500.0 - Internal Server Error
Calling LoadLibraryEx on ISAPI filter "C:\Program Files\Microsoft\Exchange Server\V14\ClientAccess\owa\auth\owaauth.dll" failed 
Detailed Error Information
Module IIS Web Core 
Notification Unknown 
Handler StaticFile 
Error Code 0x800700c1 
Requested URL http://localhost:443/ 
Physical Path C:\inetpub\wwwroot 
Logon Method Not yet determined 
Logon User Not yet determined 
Most likely causes:
•IIS received the request; however, an internal error occurred during the processing of the request. The root cause of this error depends on which module handles the request and what was happening in the worker process when this error occurred.
•IIS was not able to access the web.config file for the Web site or application. This can occur if the NTFS permissions are set incorrectly.
•IIS was not able to process configuration for the Web site or application.
•The authenticated user does not have permission to use this DLL.
•The request is mapped to a managed handler but the .NET Extensibility Feature is not installed.
 Things you can try:
•Ensure that the NTFS permissions for the web.config file are correct and allow access to the Web server's machine account.
•Check the event logs to see if any additional information was logged.
•Verify the permissions for the DLL.
•Install the .NET Extensibility feature if the request is mapped to a managed handler.
•Create a tracing rule to track failed requests for this HTTP status code. For more information about creating a tracing rule for failed requests, click here. 
 Links and More InformationThis error means that there was a problem while processing the request. The request was received by the Web server, but during processing a fatal error occurred, causing the 500 error. 
View more information »

Microsoft Knowledge Base Articles:

•294807

Now, nobody can access the Outlook Web App.

I've tried this https://social.technet.microsoft.com/Forums/lync/en-US/8b18c94b-5c2a-48ad-8ac0-06de12463f6b/owaauthdll-isap-filter-causing-problemshelp?forum=exchangesvrclientslegacy

and the scripts for 32 and 64 bit, and enabling 32 bit apps in IIS, checking the permissions on the folder, and restarting everything, and the precondition-bitness thing, nothing helps.

Nothing else is in the event log either.

I even REINSTALLED IIS and the Client Access Role. Nothing changed.

Is it because of the policy reset?

What can I do?

I do not want to restore from a backup, because that would put back the changes to the policies I just did and I would be going in circles.

Help please, ASAP.