Transaction was deadlocked on lock resources

I have this class which allow to send update request to the database through Dapper in Serializable transaction:

    public async Task<int> UpdateTable(UpdateModel model)
    {
        await using var connection = createConnection();
        await connection.OpenAsync();
        await using var tx = connection.BeginTransaction(IsolationLevel.Serializable);
        var rowsCount = await connection.ExecuteAsync(@$"

            UPDATE Table WITH (UPDLOCK, SERIALIZABLE)
            SET
                Date = @Date,
                Attempts = Attempts + 1
            WHERE
                Id = @Id
                AND DATEDIFF(MINUTE, Date, GETDATE()) < 60",
            new
            {
                model.Id,
                model.Date
            }, commandTimeout: connection.CommandTimeout, transaction: tx);
        tx.Commit();
        return rowsCount;
    }

I send 10 requests async and print result like this:

var count = 10;

while (true)
{
    var tasks = new List<Task>();
    var providerId = Guid.NewGuid();
    for (var i = 0; i < count; i++)
        tasks.Add(upsert(providerId));

    var result = Task.WhenAll(tasks.ToArray());

    result.Wait();
    Thread.Sleep(5000);
    Console.WriteLine("------------------------------------------------------------------");
}

async Task upsert(Guid id)
{
    var response = await client.Upsert(new UpsertModel
    {
        Id = id,
        Date = DateTime.Now
    });

    Console.WriteLine($"RowsCount: {response.Content}, Id: {id}");
}

When I sent 10 async requests I receive deadlocks for 9 request from 10. The message looks look like this: Transaction (Process ID 67) was deadlocked on lock resources with anot her process and has been chosen as the deadlock victim. Rerun the transaction.

Why I recieve deadlocks? And what I need to do that I can avoid deadlock?