Recursively finding all paths in a grid

Question

I am writing a small program that calculates--recursively--all paths to (0,0) on the grid given some walls that need to be avoided. The grid looks something like this:

 . . . . . . . . . . .
 | . . | . . . . . . .
 . . | . . . . . . . .
 . . - - - . . - - - -
 . | . . . . . | . . .
 . . . . . | . | . . .
 . . . . . . - - . . .
 . - - - . . . | . . .
 . | . . . . . | . . .
 . | . . . . . . . . .
 . . . | . . . . . . O

You must get to the origin without ever increasing distance to the origin in your path.

I have written this code to find all paths:

int recursive_find_path(unsigned int x, unsigned int y, unsigned int distance, std::vector<std::vector<GRID_STATUS> > blocked_grid){
  //if(x>blocked_grid.size()-1 or y>blocked_grid[x].size()-1 or x<0 or y<0 or x+y > distance or blocked_grid[y][x] == GRID_BLOCKED or blocked_grid[y][x] == GRID_TRAVELLED)
  if(x>blocked_grid.size()-1 or y>blocked_grid[x].size()-1 or x<0 or y<0 or x+y<distance or blocked_grid[y][x] == GRID_BLOCKED){
    return 0;
  }
  if(blocked_grid[y][x] == GRID_TRAVELLED){
    return 0;
  }
  if(x==0 and y==0){
    return 1;
  }
  blocked_grid[y][x] = GRID_TRAVELLED; // set position to 'travelled' on to avoid infinite recursion
  return recursive_find_path(x-1,y, distance-1,blocked_grid)+recursive_find_path(x,y-1, distance-1, blocked_grid)+recursive_find_path(x+1,y, distance-1, blocked_grid);
}

NOTE: GRID_TRAVLLED and GRID_BLOCKED are values defined elsewhere in the program but essentially are just tokens to indicate that there is a wall or the point has been travelled on.

However, when running, the program outputs that there are zero paths! Admittedly, I am not sure how many paths there are but I can at least count a few thus it can't be zero.

Does anyone know what is going wrong here?

Thanks in advance

edit

 . . . . . . . . . . . . . . . . . . .
 X . . X . . . . . . . . . . . . . . .
 . . X . . . . . . . . . . . . . . . .
 . . X X X . . X X X X . . . . . . . .
 . X . . . . . X . . . . . . . . . . .
 . . . . . X . X . . . . . . . . . . .
 . . . . . . X X . . . . . . . . . . .
 . X X X . . . X . . . . . . . . . . .
 . X . . . . . X . . . . . . . . . . .
 . X . . . . . . . . . . . . . . . . .
 . . . X . . . . . . . . . . . . . . .
 . . . . . . . . . . . . . . . . . . .
 . . . . . . . . . . . . . . . . . . .
 . . . . . . . . . . . . . . . . . . .
 . . . . . . . X . . . . X . . . . . .
 . . . . . . . X . . . . . X X X X X X
 . . . . . . . X . . . . . . . . . . .
 . . . . . . . X . . . . . . . . . . .
 . . . . . . . X . . . . . . . . . X S

Using this grid, I get an infinite loop.... updated code:

  if(x>blocked_grid.size()-1 or y>blocked_grid[x].size()-1 or x<0 or y<0 or blocked_grid[y][x] == GRID_BLOCKED){
    return 0;
  }
  if(x==0 and y==0){
    return 1;
  }
  return recursive_find_path(x-1,y,blocked_grid)+recursive_find_path(x,y-1, blocked_grid);
}

after letting it sit for a while it did return 540. I am almost certain there can't be 540 paths in this case