Hello again,
For a virtual to have information in SIM the normal way is that the ESX server is scanned and from that point the root or rootlike account logs on onto the ESX server and collects info on the virtuals running on the ESX server. So perhaps the credentials used for this datacollection are changed and thus the datapolling can't logon to get new info like OS versions.
If you changed the root account you should update the root account used in SIM to discover the ESX servers.
I know you don't have ESX but i guess it works the same way. SSH is enabled by default so perhaps someone disabled it for a reason.