Passing derived class to base function

I’m having trouble passing a derived class to a function which accepts the base class as argument. The base class is consists of “obstacles” which are to be placed on a “board” void Board::setvalue(int length, int width, Obstacle& obstacle);

However, this causes the compiler to give the “no known conversion for argument…”-error. Reading up around the site i found that i should be passing the derived object as a const, this however causes problems because a const can’t be assigned to the board (since it holds pointers to non-const Obstacles).
In turn, changing Board to hold const Obstacles causes a lot of issues elsewhere in the project, especially with the operator<< of Board and Obstacle.
I have tried passing the objects as consts and then using Obstacle ob = new obstacle(the const obstacle) but this made them generic Obstacle objects rather than Player/Barrel/Wall objects.

Is there any way to pass these objects as non-consts or assigning them as non-consts? i tried using const_cast() but this caused undefined behaviour.

An example of the function call:

Board_->setvalue(x, y, Player(data, moveable, x, y));

Here is my code:

The base class

class Obstacle
    Obstacle* _properlyinitialized;
    string Name;
    bool Moveable;
    int x;
    int y;
    Obstacle(string Name, bool Moveable, int x, int y);
    virtual ~Obstacle();
    bool properlyInitialized();
    friend std::ostream& operator<<(std::ostream& stream, Obstacle& Obstacle);

An example of the derived classes (other derived classes don't have special functions yet)

class Player: public Obstacle
    Player(string Name, bool Moveable, int x, int y):Obstacle(Name, Moveable, x, y){this->_properlyinitialized = this;};
    /*void Moveleft();
    void Moveright();
    void Moveup();
    void Movedown();*/

The Board class header

class Board
    Board* _properlyinitialized;
    int length;
    int width;
    Obstacle * * * playfield;

                "Object wasn't initialized when calling object");
    Board(int length, int width);
    bool properlyInitialized();
            "Object wasn't initialized when calling properlyinitialized");
    void clear();
    const int getLength();
    const int getWidth();
    Obstacle*** getBoard();
    Obstacle* getTile(int length, int width);
    void setvalue(int length, int width, Obstacle& obstacle);
    friend std::ostream& operator<<(std::ostream& stream, Board& Board);

std::ostream& operator<<(std::ostream& stream, Board& Board);

And finally, the setvalue function.

void Board::setvalue(int length, int width, Obstacle& obstacle)
    this->playfield[length][width] = &obstacle;//value;

I'm happy to provide more code if needed.