Javascript working on desktop but not on mobile

This script works fine on desktop but won’t work on mobile and gives me no errors in the console.

Here is my html:

<p><select id="feet">
        <option value="0">0</option>
        <option value="4">4</option>
        <option value="5">5</option>
        <option value="6">6</option> 
    </select> feet <select id="inches">
        <option value="0">0</option>
        <option value="1">1</option>
        <option value="2">2</option>
        <option value="3">3</option>
        <option value="3">4</option>
        <option value="3">5</option>
        <option value="3">6</option>
        <option value="3">7</option>
        <option value="3">8</option>
        <option value="3">9</option>
        <option value="3">10</option>
        <option value="3">11</option> 
    </select> inches <select id="weight">
        <option value="0">0</option>
        <option value="100">100</option>
        <option value="105">105</option>
        <option value="110">110</option>
        <option value="115">115</option>
        <option value="120">120</option>
        <option value="125">125</option>
        <option value="130">130</option>
        <option value="135">135</option>
        <option value="140">140</option>
        <option value="145">145</option>
        <option value="150">150</option>
        <option value="155">155</option>
        <option value="160">160</option>
        <option value="165">165</option>
        <option value="170">170</option>
        <option value="175">175</option>
        <option value="180">180</option>
        <option value="185">185</option>
        <option value="190">190</option>
        <option value="195">195</option>
        <option value="200">200</option>
        <option value="205">205</option>
        <option value="210">210</option>
        <option value="215">215</option>
        <option value="220">220</option>
        <option value="225">225</option>
        <option value="230">230</option>
        <option value="235">235</option>
        <option value="240">240</option>
        <option value="245">245</option>
        <option value="250">250</option>
    </select> lbs. <input id="submit-btn" type="submit" value="Enter"></p>
<h3>BMI: <span id="output">0</span></h3>

And here is the javascript:

function computeBMI() {
  //Obtain user inputs
  var feet = Number(document.getElementById("feet").value);
  var inches = Number(document.getElementById("inches").value);
  var weight = Number(document.getElementById("weight").value);

  var height = Number(inches + (feet * 12));

  //Perform calculation
  var BMI = weight / Math.pow(height,2);
  var BMI = BMI * 703;

  //Display result of calculation
  document.getElementById("output").innerText = Math.round(BMI * 100)/100;
}
  
document.getElementById("submit-btn").addEventListener("click", computeBMI);