According to https://matomo.org/faq/tag-manager/create-a-container-in-matomo-tag-manager/
When you create a new site in Matomo (most of the time a container will equal one website), the Tag Manager will automatically pre-configure a container with a Matomo tracking code tag for you (you will find this tracking code within the Tracking code menu in the backend)
A new site was created in Matomo. On the Dashboard page, the Matomo Tag Manager section is all greyed out, with no containers found. On the Tag Manager page, also no containers found.
My client has done this for a few websites, and all have exactly the same problem.
While I can create a new container, why is this happening? And are there any instructions anywhere on what exactly would be needed to be added to a new container to match what should have been the defaults? (I.e. just the tracking code, but there are so many options to fill in when adding a new tag, it doesn’t seem clear).