When you finish all these steps and try accessing the "Operation Center app" and having the "Access denied" page. Please do the following:
On your browser go to "Enterprise application" on your "Azure Ad", find and select the "LiveTiles-Backoffice-API".
Find a menu option "Users and groups", and make sure that your user is present there and has a "Admins" or "Editors" role, if not please select it and press the "Edit assignment" button on the top. And assign you a more appropriate role "Admins" or "Editors".
Once done that you can get back to the app and refresh the page, if the "Access danied" page persists please clean the site data. To do that press F12, chose Application tab, and on Storage press "Clean Site data" button.