EntryPointNotFoundException - .so plugin (Linux)

I'm trying to use a .so plugin which I compiled using Linux but i keep getting EntryPointNotFoundException

Here's a sample of the c++ code.

cpp:

 #include <rosgraph_msgs/Clock.h>
 #include <unistd.h>
 #include <thread>
 #include "ros_interface.hpp"
 #include "node.hpp"
 
 // Default initializer
 ros_interface::ros_interface() {
     // NOP
 }
 
 // Initialize the ROS communication interface
 ros_interface::ros_interface(int argc, char** argv, string node_name) {
     // ROS initialization
     ros::init(argc,argv,node_name);
 
     // Set the time simulation as in "/clock"
     system("rosparam set /use_sim_time true");
 
     // Initialize the pointer to clocker
     c = new clocker;
 
     // Set publisher on clocker
     c->pub_clock = c->nh.advertise<rosgraph_msgs::Clock>("/clock",1);
 
 }
 
 // Destructor
 ros_interface::~ros_interface() {
     // Delete all node pointers in nodes_ptr
     for(auto x : nodes_ptr) delete *((node**) x);
 
     // Delete clock struct pointer
     delete(c);
 }
 
 extern "C" void initialize() {
     instance = new ros_interface(0, 0, "instance");
 }
 
 // Lots of other stuff

And the hpp:

 #ifndef ROS_INTERFACE_H
 #define ROS_INTERFACE_H
 
 #include <string>
 #include <vector>
 
 // Position data type
 struct position {
     double x;       // position in x
     double y;       // position in y
     double z;       // position in z
     double roll;    // lateral axis (X)
     double pitch;   // longitudinal axis (Y)
     double yaw;     // vertical axis (Z)
 };
 
 // Velocity data type
 struct velocity {
     double x;       // velocity in x
     double y;       // velocity in y
     double z;       // velocity in z
     double roll;    // lateral axis angular velocity
     double pitch;   // longitudinal axis angular velocity
     double yaw;     // vertical axis angular velocity
 };
 
 extern "C" void initialize(); 
 extern "C" void addNode(int id, int type, std::string target, position init_pose); 
 extern "C" void setVelocity(int id, velocity msg); 
 extern "C" position getPos(int id); 
 extern "C" void setClock(float dt); 
 extern "C" bool rosOk(); 
 
 // Node class to ROS interface
 class ros_interface {
 public:
     // Default initializer
     ros_interface();
 
     // Initialize the ROS communication interface
     ros_interface(int argc, char** argv, std::string node_name);
 
     // Destructor
     ~ros_interface();
 
 // And more stuff...

And here's the c# code used in unity:

     [DllImport("ros_interface")]
     private static extern void initialize();
 
     [DllImport("ros_interface")]
     private static extern void addNode(int id, int type, string target, Pose init_pose);
 
     [DllImport("ros_interface")]
     private static extern void setVelocity(int id, Pose p);
 
     [DllImport("ros_interface")]
     private static extern bool rosOk();
 
 
     // Use this for initialization
     void Start()
     {
         initialize();
     }

I build it sucessfully with unity and then run it on linux, but i get the following error when calling the initialize method:

EntryPointNotFoundException: initialize

I did some research, this error means that the initialize method was not found on the plugin, but the method seems to be there and I haven't found a solution. The same error will pop if I try to call any of the methods from the .so plugin.

What can I do to make this plugin work?