I’am having a issue with omnet++ when running my first project and I don’t get where the problem is

the error is : <!> Class “BaseStation” not found — perhaps its code was not linked in, or the class wasn’t registered with Register_Class(), or in the case of modules and channels, with Define_Module()/Define_Channel() — in module (omnetpp::cModule) SimulationNetwork (id=1), during network setup

I verified BaseStation calls are all fine, but I cant get where is the error.
It would be great if you can help me, it will really save my life.

Thank you in advance.

I have 3 ned files : Node.ned, BaseStation.ned and Network.ned :

Node.ned :

package _6g_simulation;

simple Node {
    parameters:
        int id;
        @display("i=device/laptop");
    gates:
        inout inoutg[];
}

BaseStation.ned :

package _6g_simulation;

simple BaseStation {
    parameters:
        @display("i=device/server");
    gates:
        inout inoutg[];
}

Network.ned :

package _6g_simulation;
import _6g_simulation.BaseStation;
import _6g_simulation.Node;

network SimulationNetwork
{
    submodules:
        basestation: BaseStation {
            @display("p=40,111");
        }
        edgeNode[5]: Node {
            @display("p=150,38");
        }
        endUser[10]: Node {
            @display("p=241,64");
        }
    connections allowunconnected:
        // Connect base station to edge nodes
        for i=0..4 {
            basestation.inoutg[i] <--> edgeNode[i].inoutg[0];
        }
        // Connect edge nodes to end users
        for i=0..9 {
            edgeNode[i % 5].inoutg[0] <--> endUser[i].inoutg[0];
        }
}

omnetpp.ini :

[General]
network = _6g_simulation.SimulationNetwork

My expectation is to run the simulation without any problem and I can see the nodes and the base station network on