Network Issue

I have one PC on our WAN that can’t access one specific server. Here are the specifics on this.
This PC can access all network resources except one server. This same server can access all network resources except the afore mentioned PC.
Pinging any networked device from the PC returns an appropriate reply except when pinging the one server, Request Timed Out. Pinging any network device from the server also returns an appropriate reply except with pinging this one PC, Request Timed Out. All other PCs and servers on the network can access and ping both the affected PC and server without any issues.