Dell PowerEdge (Windows Server 2016 Os) Logon Issue

I am farly new to the server sphere, so please bear with me.

I have  2 *1TB hdd drives configured to RAID1 on my Poweredge T110 II server.I recently  installed windows server 2016 evalution version with one Administrator account on the server .

Afterwards I disabled the public firewall to allow remote  login via RDP , I also installed Teamviewer as back up and left it at that.Tested this and it was working fine as I was able to access the server remotely via RDP for a week. Yesterday upon trying to access the server remotely it wouldn't let me, so I hooked a mouse and keyboard to directly  login but  my Administrator  password is no longer  working and there is a new  user account named Microsoft1 which I did not set up .

I am confused at this point and not sure as to wheather this is an issue with the BIOS configuartion  or a windows updates bug. I have set the server to download and install windows updates automatically.