Trying to get users displayName, returning unknown user

    const loggingData = JSON.parse(fs.readFileSync("logging.json", "utf8"));
    const users = Object.keys(loggingData).sort(function(a, b) {
      return loggingData[b].tweets - loggingData[a].tweets;
    }).slice(0, 10);
    if (users.length == 0) {
      await interaction.reply("No tweets logged");
    } else {
      const leaderboard = new EmbedBuilder()
        .setTitle("Tweet Leaderboard")
        .setColor("#54a329")
        .setFooter({
          text: "redacted",
          iconURL: "redacated",
        })
        .setTimestamp();
      for (let i = 0; i < users.length; i++) {
        let user = users[i];
        let position = i + 1;
        let numTweets = loggingData[user].tweets;
        let member = interaction.guild.members.cache.get(user);
        let displayName = member ? member.displayName : "Unknown User";
        leaderboard.addFields({
          name: position + ". " + "<@" + displayName + ">",
          value: numTweets + " tweets logged.",
          inline: false
        });
      }
      await interaction.reply({
        embeds: [leaderboard]
      });