You'll probably have already run the  sfc /scannow command in an elevated command prompt. Chances are, it found corrupt files and was unable to correct them.

When you purchase an OVH dedicated server and select to install ESXi, you'll receive a temporary password. What they fail to mention is that the password you're sent expires after around 30 days. OVH is unable to reset the password and does not have a record of it. Their response is to reinstall the ESXi server and copy off any data from your ESXi hosts beforehand. Obviously, this is a very poor response from OVH and there was no way in the world we were about to perform a full reinstallation.

We ran into an issue recently with transferring files between a server and a workstation. They were connected via openVPN client and a pfsense router running OpenVPN server. We found that when pinging the pfsense from the connected client, pings worked fine. The main issue came however when we attempted to copy a file from the server to the client. 

The most common cause of being unable to install an optional feature on Windows server is that you have previously configured up Microsoft WSUS (Windows Server Update Services).