Google Analytics with Google Tag Manager not reporting properly on subdomains

Question

I have a site with 3 subdomains with the same Google Tag Manager and Google Analytics tracking ID. I created 3 views on the property, I applied the proper inclusion filters so I can focus each view on its counterpart subdomain.

GTM is firing GA on the three subdomains and the GA debugger is showing that it is tracking (I tried recording and it worked, I tried GA plugin and there are no errors).

The problem: One of the subdomains is reporting everything (all subdomains)! Even with the proper inclusion filter in place. The 2 other subdomains are reporting nothing.

Note that my inclusion filter is equal sub1.example.com (and the same view is reporting on sub2.example.com and sub3.example.com)

I spent 6 hours so far, reading documentation and trying different options to no avail.

Why would be a filtered view for one subdomain show stats for the other subdomains? Why would the other subdomains show nothing? Would this be related somehow to GTM?

• GTM id is the same across the domains and not duplicated and matches the account number
• GA snippet is not included on the pages and the id is double checked
• The three subdomain settings are exactly the same with only the inclusion filter being different

Answer 1

Make sure that you disable UserId Tracking when you create a View. Enabling UserId Tracking will exclude all analytics without it being set.