Minesweeper (part 15/16)

I can't fullfill the requestst - when I try this:

private void restart()  {
 isGameStopped = false;
        countClosedTiles = SIDE * SIDE;
        score = 0;
        setScore(score);
        countMinesOnField = 0;
}

I got following error: The createGame() method must clear all items (flags, mines, numbers) from the playing field. Use the setCellValue(int, int, String) method. Pass an empty string as the last argument. When I try to add to the code following piece:

for (int y=0; y<SIDE; y++)  {
            for (int x=0; x<SIDE; x++)  {
                setCellValue(x, y, "");
            }
        }

I got a lot of weird errors, for instance, that I have to assign false to isGameStopped field. But I am do doing this! My game works correctly, but I can't pass the tests. :-(