If we’ve (or you) have installed Google Tag Manager (GTM) on the site, then you don’t need to insert Google Analytics onto the site itself. We’ll inject Google Analytics using GTM, and putting a tag on yourself will actually cause us to have duplicate tags on the site.
If analytics is already on the site, please remove it so we can install it using Google Tag Manager (if you've already installed it using GTM then you can leave it on).