Had the same problem with 80%, I think the issue was the way how you calculate the 'cool treshold' and specifically for the case there was just one digit. Here two variants with 80% and 100%:

(80%):

using System;
using System.Linq;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace emoji
{
    class Program
    {
        static void Main(string[] args)
        {
            string numberPattern = @"(?<number>[0-9])";
            string emojiPattern = @"(:{2}|\*{2})(?<emoji>[A-Z][a-z]{2,})\1";

            Regex numberRegex = new Regex(numberPattern);
            Regex emojiRegex = new Regex(emojiPattern);

            string input = Console.ReadLine();

            MatchCollection numberMatches = numberRegex.Matches(input);

            MatchCollection emojiMatches = emojiRegex.Matches(input);

            var numbers = new List<int>();

            foreach (Match match in numberMatches)
            {
                int number = int.Parse(match.ToString());

                numbers.Add(number);
            }

            int coolTotal = 0;
            
            for (int i = 0; i < numbers.Count; i++)
            {
                if (i == 0)
                {
                    coolTotal += numbers[i] * numbers[i + 1];
                    i++;
                }
                else
                {
                    coolTotal *= numbers[i];
                }
            }

            var emojiList = new Dictionary<string, int>();

            foreach (Match match in emojiMatches)
            {
                string emoji = match.Groups["emoji"].ToString();
                char[] letters = emoji.ToCharArray();
                int number = letters.Sum(x => (int)x);
                string trueEmoji = match.ToString();

                if (!emojiList.ContainsKey(trueEmoji))
                {
                    emojiList.Add(trueEmoji, number);
                }
            }

            Console.WriteLine($"Cool threshold: {coolTotal}");


            if (emojiList.Any())
            {
                Console.WriteLine($"{emojiList.Count} emojis found in the text. The cool ones are:");
                foreach (var (name, number) in emojiList)
                {
                    if (number > coolTotal)
                    {
                        Console.WriteLine($"{name}");
                    }
                }
            }
        }
    }
}

(100%):

using System;
using System.Linq;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace emoji
{
    class Program
    {
        static void Main(string[] args)
        {
            string numberPattern = @"(?<number>[0-9])";
            string emojiPattern = @"(:{2}|\*{2})(?<emoji>[A-Z][a-z]{2,})\1";

            Regex numberRegex = new Regex(numberPattern);
            Regex emojiRegex = new Regex(emojiPattern);

            string input = Console.ReadLine();

            MatchCollection numberMatches = numberRegex.Matches(input);

            MatchCollection emojiMatches = emojiRegex.Matches(input);

            var numbers = new List<int>();

            foreach (Match match in numberMatches)
            {
                int number = int.Parse(match.ToString());

                numbers.Add(number);
            }

            int coolTotal = 0;

            if (numbers.Count >= 2)
            {
                for (int i = 0; i < numbers.Count; i++)
                {
                    if (i == 0)
                    {
                        coolTotal += numbers[i] * numbers[i + 1];
                        i++;
                    }
                    else
                    {
                        coolTotal *= numbers[i];
                    }
                }
            }
            else
            {
                coolTotal = numbers.Sum();
            }

            var emojiList = new Dictionary<string, int>();

            foreach (Match match in emojiMatches)
            {
                string emoji = match.Groups["emoji"].ToString();
                char[] letters = emoji.ToCharArray();
                int number = letters.Sum(x => (int)x);
                string trueEmoji = match.ToString();

                if (!emojiList.ContainsKey(trueEmoji))
                {
                    emojiList.Add(trueEmoji, number);
                }
            }

            Console.WriteLine($"Cool threshold: {coolTotal}");

            if (emojiList.Any())
            {
                Console.WriteLine($"{emojiList.Count} emojis found in the text. The cool ones are:");
                foreach (var (name, number) in emojiList)
                {
                    if (number > coolTotal)
                    {
                        Console.WriteLine($"{name}");
                    }
                }
            }
        }
    }
}