Two Macs on network, cannot see each other.

[macasnak]

I have two Macs on network. File sharing on. SMB /AFP enabled.
They were able to communicate before.
I have made changes like adding Mojave to one, adding apps etc.. to both.
I am trying to find out, what are/ would be the processes/ apps that may be blocking / stopping the two communicating/ showing on the network?...

 

[kschendel]

I'd start by going into network preferences and making sure that both are on the same subnet. (meaning, both are 10.x.x.x, or both are 192.168.y.x and both have the same "y".)

 

[macasnak]

Both have the same subnet mask and both have the same IP apart from the last number as expected.
Only difference is DNS Server. They have different OS on. Not sure if that is what would make them different.