Can't see one computer on network (but it can see others)

[Jlovel7]

I'm creating a local network for several students to collaborate in Revit.  A desktop is serving as the central "server" where the files are being shared from.  This computer can see the others on the network but the others cannot see it (which is what needs to happen to access the central files).  One of the other computers had already been mapped to find the network drive and it is able to connect without any issues, but no new computers can be mapped because they cannot see it.  However, they can see it listed under windows media player so I know there's at least some connection being made.  I just can't find the right settings to play with to make them visible.  Previously It was working but I've seemed to have accidentally messed it up some how.  Any help would be great! Let me know if you need more information from me.  

[pwn_intended]

Are you mapping the share by IP address directly or attempting to do it with hostname only?

[Jlovel7]

To be honest, I'm not sure.  We're just plugged into ethernet ports in our studio (that I assume all travel back to one switch) and then turning network sharing on. Previously we were able to see each other but now the "server" can only see all of the other computers and not the other way aorund.  So I'm guessing that some setting on the "server" got messed up accidentally.  And all of the other computers that would connect to the server can see the listed windows media library, so I know that at least some kind of connection is being made.