AdSense Plugin – Access Denied

I just activated this plugin (1.1 version). I changed the Adsense code to reflect my own account but when I tried to save it, I got a “forbidden” message that I don’t have permission to access wp-admin/options-general.php on my server.

Is this related to the theme I’m using?

My blog can be viewed at https://nsnssite.com/enjoylifemore/

I have temporarily deactivated the plugin.