error: no matching function for call to 'Board::Board()'
means that class Board
is missing the deafault constructor. In the constructor of Solver
you are probably doing something like:
Solver::Solver(const Board &board_c, int max_moves_c) {
Board b; // <--- can not construct b because constructor is missing
...
}
so you either have to define the default constructor or invoke the appropriate constructor with some arguments.
"And then it lists the candidates which are the Board constructors."
That's because compiler wants to help you so it lists possible constructors that are actually available (defined).