Well,as it turned out SNMP (simple Network Management Protocol) was reason for making one of MFP shows offline in windows 7-64bit.
in the properties page,port ,Configure port ..just uncheck the SNMP and the printer will be online again.

As you may know SNMP is a way of getting information from network devices (such as routers, servers and printers), mainly for the purposes of finding out if there are any problems with the devices. A number of networked printers implement SNMP, and will respond to SNMP queries with information, but some don’t.
what is unclear about this ,is why another bizhub C552 has SNMP checked and works properly , but the other one could not communicate with this protocol !!
I even disconnected bizhub C552 from network and restart system in order to find out if the presenting two of them makes this conflicts but still C452 shows offline when SNMP is active.

So still looking for the reason , but the issue is solved!
Thanks