Authorization Lifecycle on published add-on is not working - google-apps-script

Question

Have a problem with my add-on that should, but not creating a menu items in Add-ons on Google Sheets and Docs on install from the store until the page is refreshed.
According to Google Support I should look in to the following:
"Usually this is caused by a problem with the Authorization Lifecycle, specifically the opening stage.
The most common culprit is a global variable in the code that tries to access Google services without authorization, like:
var doc = DocumentApp.getActiveDocument();
See the documentation:
Warning: When your onOpen(e) function runs, the entire script is loaded and any global statements are executed. These statements execute under the same authorization mode as onOpen(e) and will fail if the mode prohibits them. This preventsonOpen(e) from running. If your published add-on fails to add its menu items, look in the browser's JavaScript console to see if an error was thrown, then examine your script to see whether the onOpen(e) function or global variables call services that aren't allowed in AuthMode.NONE."
I have no idea what and how should I deal with this as my add-on was not created by me. I can do minor things, but this is something that I cannot handle on my own and really need your help please.
Hear is my script:
function onOpen(e) {
SpreadsheetApp.getUi().createAddonMenu()
.addItem('Browse Templates', 'browseTemplates')
.addToUi();
}
function onInstall(e) {
onOpen(e);
}
function browseTemplates(){
collectBasicData();
// Display a modal dialog box with custom HtmlService content.
var htmlOutput = HtmlService
.createTemplateFromFile("Gallery").evaluate()
.setWidth(700)
.setHeight(510);
SpreadsheetApp.getUi().showModalDialog(htmlOutput, 'Spreadsheet123 - Template Vault');
}
function collectAllData(){
var sheet = SpreadsheetApp.openById(SPREADSHEET_ID).getSheetByName(DATA_SHEET);
DATA = sheet.getDataRange().getValues();
return DATA;
}
function collectBasicData(){
var sheet = SpreadsheetApp.openById(SPREADSHEET_ID).getSheetByName(PIVOT_SHEET);
var tabSheet = SpreadsheetApp.openById(SPREADSHEET_ID).getSheetByName(TAB_SHEET);
BASIC_DATA = {
"tab_about" : getValue(tabSheet,"B1"),
"tab_help": getValue(tabSheet,"B2"),
"pivot":sheet.getDataRange().getValues()
};
return false;
}
function getValue(sheet,addr){
return sheet.getRange(addr).getValue().toString().replace(/^\s+|\s+$/g, '');
}
function createACopy(id){
var docName = DocsList.getFileById(id).getName();
return DocsList.getFileById(id).makeCopy(docName).getUrl();
}
function insertInCurrent(id){
var destinationSpreadSheet = SpreadsheetApp.getActiveSpreadsheet();
var sourceSheets = SpreadsheetApp.openById(id).getSheets();
for(var i=0;i<sourceSheets.length;i++){
var sheetName = sourceSheets[i].getName();
var source = SpreadsheetApp.openById(id).getSheetByName(sheetName);
source.copyTo(destinationSpreadSheet).setName(sheetName);
}
}
I have looked in to the documentation on Google, but cannot understand how and where I should use it in my script.
Your help is highly appreciated and thanks in advance