Google analytics ID and tag manager

Site URL: https://www.computehub.io

Hi,

We recently talked with a google rep about out tracking (we have cross-domain tracking issues) and he suggested that we switch to using tag manager on our site.  So I injected the code in the header/footer section in squarespace and I removed the analytics ID from within squarespace via the google rep's suggestion as he said it could cause duplicate tracking. 

However, now I am seeing almost no tracking in our google analytics compared to using the built-in squarespace analytics.

My question is do I still need to have the analytics ID in squarespace or was the google rep right in having me pull it?  If it is the latter then maybe it is a tracking config issue on the google side.  I just need to understand if I should have both a google tag and the analytics ID on my website.