We shall tell you the Same. Theme has some places but theme doesn’t control the content. You can use any HTML, JavaScripts, ShortCode there but can not use PHP. You can use the ShortCode [ad Id 4332]
, too. You can try disabling your Plugins one by one if any of them are responsible for them or not. 403 Error is a Server Side issue. Not fornt-end like the theme. If you provide us one Temporary Admin ID and Password to the Technical Support we can show you the Ads putting our Google AdSense Ads there. We are confirming you again, these are not Theme Issues.
You can find these sites who are managing millions of visitors with Ads without any issue: ournewsbd.com anmnews.com alldaywow.com etc.