for (int i = 1; i < sheet.RowsCount; i++)
{
    var cells = sheet.GetRow(i).Cells;

    (...)

    // cells are strings
    if (!DateTime.TryParse(cells[1], out DateTime date))
    {
        Console.WriteLine($"Unable to parse DateTime for row {i}"); // <--- here
        continue;
    }
}

for (int i = 1; i < sheet.RowsCount; i++)
{
    var cells = sheet.GetRow(i).Cells;

    (...)

    // cells are strings
    if (!DateTime.TryParse(cells[1]), out DateTime date))
    {
        throw new Exception($"Problem with parsing DateTime at {i} row"); // <--- here
    }
}