Mogodb secondary node port not coming up

Hi

We have our mongo in a on prem. primary node we are able to connect . secondary node port is not up.
If i check rs.status() from primary ,secondary node is in not reachable state.
Tried restarting also .
I am not sure what to do to resolve this.
Any suggestion

How many nodes in your replica setup?
When you restarted secondary node did it come up successfully?
Check your mongod.log