Keyset does not exist / Identity invalid

Note: I've found several questions similar on here, but the one's that were resolved did not work for me. So I thought I'd open a new question.

I rebooted our server 2012 box, which hosts our new .net applications. After doing so, I started receiving a 503 error. Upon investigation, it seemed like an identity problem.

Before going much further, I should state that this account has worked for several months now. I've rebooted before, and everything started fine.

So I'm getting the (quite common) 5059, 5057, and 5021 errors in the log. They boil down to this:

The identity of application pool SVFileUpload is invalid. The user name or password that is specified for the identity may be incorrect, or the user may not have batch logon rights. If the identity is not corrected, the application pool will be disabled when the application pool receives its first request. If batch logon rights are causing the problem, the identity in the IIS configuration store must be changed after rights have been granted before Windows Process Activation Service (WAS) can retry the logon. If the identity remains invalid after the first request for the application pool is processed, the application pool will be disabled. The data field contains the error number.

I thought I would just ensure the password and account were correct, so I go to the application pool, select identity-> custom and ensure it's set up right. I get an error:

There was an error while performing this operation. Details: Keyset does not exist (Exception from HRESULT: 0x80090016)

This was strange to me, so I tried setting the app pool to a built in account, and it worked fine. I get this error anytime I try to set to a custom account. Also, no app pools that are using custom accounts will run.

I googled a bit, unsure which error was the one I needed to track. I have tried:

registering the account on the command line via the aspnet_ tool
Making sure the user was in the IIS_IUSRS group
changing the permissions on C:\ProgramData\Microsoft\Crypto\RSA\MachineKeys file(s)
adding a completely new user and trying to set an app pool to that users account

There was a couple other random things I tried from googling but I don't remember.

This error doesn't make sense to me, and it seems random. I need help figuring out 1) why I can't set an app pool to a custom account and 2) why the identity isn't working for my applications anymore

-Edit
I recently removed and re-added the user account I've been working with. I think that solves that problem. The problem remaining is I can't update the application pool because of the "keyset does not exist" error.

Solution

I found a couple of links that led me to a solution.

In c:\windows\system32\inetsrv\config\applicationHost.config I removed all the configProtectedData entries.

Then I removed everything in %ALLUSERSPROFILE%\Microsoft\Crypto\RSA\MachineKeys

I ran iissetup.exe /install SharedLibraries from the inetsrv directory, which resulted in a "Failed = 0x80070005"

I then was able to set up my application pools as if nothing happened.