Cannot connect over network from 1 of 4 PCs

I have a hardwired LAN with 4 pcs and a MyCloudMirror. I reinstalled Win 7 on PC#4. Now all connections work over the network and http except cannot connect from PC#4 over the network to the MyCloudMirror because user/password declined. User can logon over http. Any thoughts?

Later: this problem has been solved through spontaneous remission. Rather disturbing considering the amount of time spent on it.

Thanks for editing the post to let the community know that you were able to solve the issue.

If possible, can you please share what you did to solve the situation.