Unable to RDP into Windows Instance

Question

We had access to one of our Windows 2008 R2 machines until recently, we can't figure out what the issue is with RDP, but we are unable to access from Mac or Windows machines.  
  
On a Mac with RDP Version 10, I get the error   
"Your session ended because of an error. If this keeps happening, contact your network administrator for assistance.  
  
Error code: 0x4"  
  
With RDP Version 8, I get the error:  
"Security negotiation Error: TLSRequired(1)"  
  
Launching a new instance from a saved AMI gives the same results.

Answer

With the help of Louis T. at Amazon tech support we discovered that it was corrupted RSA Machine Keys.  
  
Steps are:  
- Access corrupt drive via another EC2 instance  
- Rename MachineKeys folder for back-up  
- Create a new empty MachineKeys folder  
- Assign permissions to new folder  
- Reattach to original EC2 intstance  
  
Instructions for the EC2 instance/folder naming are in this pdf: https://drive.google.com/open?id=1glgqgHm6SycPKPlV__WcQzWg1AeJMs78  
  
Set permissions via CMD with "Run as Administrator"  
takeown /f "D:\ProgramData\Microsoft\Crypto\RSA\MachineKeys" /a /r  
	icacls D:\ProgramData\Microsoft\Crypto\RSA\MachineKeys /t /c /grant "NT AUTHORITY\System:(F)"  
	icacls D:\ProgramData\Microsoft\Crypto\RSA\MachineKeys /t /c /grant "NT AUTHORITY\NETWORK SERVICE:(R)"  
	icacls D:\ProgramData\Microsoft\Crypto\RSA\MachineKeys /t /c /grant "BUILTIN\Administrators:(F)"

Unable to RDP into Windows Instance

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