[BUTTON DISAPPEARANCE] I am updating TaskviewLayout, but problem occurred

Problem is that button disappears if restarting! Please, advise me.
I used legacy API because of being difficult to port my addon to Lightning.

XUL file is as below.
<?xml version=“1.0”?>
<?xml-stylesheet href=“taskviewlayout.css” type=“text/css”?>
<overlay id=“ltnToolbarOverlay” xmlns=“http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul”>
<script type=“text/javascript”
src=“taskviewlayout.js”/>
<script type=“text/javascript”
src=“tv4.js”/>
<toolbarpalette id=“TaskToolbarPalette”>
<toolbarbutton id= “taskviewlayout” tooltiptext=“Taskview Layout” class=“toolbarbutton-1 chromeclass-toolbar-additonal” label=" Taskview layout" type=“menu-button”>
<menupopup>
<menuitem id=“menuitem1” label=“View to put task view up” onclick=“tv1();”/>
<menuitem id=“menuitem2” label=“View to put task view neutrally” onclick=“tv2();”/>
<menuitem id=“menuitem3” label=“View to put task view vertically” onclick=“tv3();”/>
</menupopup>
</toolbarbutton>
</toolbarpalette>
</overlay>

Script file is as below.
function tv1() {
var layoutContainer = document.getElementById(‘calendar-task-details-container’);
var layoutABox = window.document.getElementById(‘task-addition-box’);
window.document.getElementById(‘calendar-task-box’).insertBefore(layoutContainer, layoutABox);
document.getElementById(‘calendarDisplayDeck’).style.flex = ‘1’;
};

function tv2() {
var layoutContainer = document.getElementById(‘calendar-task-details-container’);
window.document.getElementById(‘calendar-task-box’).appendChild(layoutContainer);
document.getElementById(‘calendarDisplayDeck’).style.flex = ‘1’;
};

function tv3() {
var layoutContainer = document.getElementById(‘calendar-task-details-container’);
document.getElementById(‘calendarDisplayDeck’).style.flex = ‘0 2 0’;
document.getElementById(‘calendarContent’).appendChild(layoutContainer);
};

Sincerely.

Sungho Hwang.

It is stable in 71.0 beta version.
So, I changed strict min version to 71.0 in manifest.json.
Soon, version 55.6 is updated for Thunderbird 71.0 beta.