When installing both google_analytics and google_tag, the ga module is no longer functional due to the google_tag_module_implements_alter hook unsetting the ga hook. This either should not be there, or there should be some support for the google analytics account number.
In the very least, this conflict needs to be much more widely communicated to the user on the edit form or present some type of message in the site "status report" page. There is no information on either module page indicating any problem installing both modules together.
Remove the hook unset or support it in the google_tag.tag_container_resolver service.
Active
2.0
Code
I assume there must have been some rationale for unsetting GA page attachments originally, so I don't know if removing that code is the best option, but here's a patch for 2.x branch that does that for anyone who needs it.