HTML CSS Error - Audio Toggle Button not working

Hi - I am at final approval of a site and this last error is driving me mad, something is conflicting

A > AUDIO toggle button not working

B > AUDIO toggle button works

Something is breaking… I think there may be a container / layering conflict.
Any help would be MOST appreciated!

You do not have the same id on the video element on page 2 as you do on page 1.

audio.js:7 Uncaught TypeError: Cannot read property 'muted' of null
at toggleMute (audio.js:7)
at HTMLButtonElement.onclick (index2.html:63)
var video = document.getElementById("showreel");
<video class="reel" autoplay="" muted="" loop="">
	<source src="PJMProductions_Showreel.mp4" type="video/mp4">
	<source src="PJMProductions_Showreel.webm" type="video/webm">
	<source src="" type="video/mov">