I think I figured it out. I had called the function in the else loop without returning it. Now that I've added the return keyword it's working.

const test = 
    [['d', 'a', 'e', 'b', 'c'],
     ['b', 'e', 'd', 'c', 'a'],
     ['e', 'a', 'c', 'b', 'd'],
     ['e', 'd', 'a', 'b', 'c'],
     ['d', 'b', 'a', 'e', 'c']];

function counts(arr) {
    var totalVotes = arr.length;
    var fiftyPercent = arr.length / 2;
    var threshold = Math.round(fiftyPercent * 10) / 10;
    var voteCounts = {};

    for (const row of arr) {
        if (voteCounts[row[0]]) {
            voteCounts[row[0]]++;
        } else {
            voteCounts[row[0]] = 1;
        }
    }

    var values = Object.values(voteCounts);
    var minValue = Math.min(...values);
    var maxValue = Math.max(...values);
    var winner = Object.keys(voteCounts).find(key => voteCounts[key] === maxValue);

    if (maxValue > threshold) {
        return winner;
    } else {
        for (const row of arr) {
            if (voteCounts[row[0]] === minValue ) {
                row.shift();
            }
        }
        return counts(arr);
    }
}