|Please describe as best you can what connects to what. |
For example do you see a router and modem or is it a combo unit or just a modem?
How many lan ports on this router? Is the server and two pcs connected to it?
Do you get internet to the server?
Where did you get the security popup saying there may be a security issue?
Can the pcs ping the server? Each other?
A one sentence question will result in a one sentence answer.