I have a custom report set in Google Analytics and when I view the metrics via Country, it's telling me the lowest page views didn't have any sessions but a small number of page views. I'm trying to get my head around sessions are really entrances, but I can't see how this applies when viewing by country? The custom report only tracks users who are logged in to my site and not the register/sign in page.
The official Analytics documentation states "Sessions is incremented on, and associated with, the first hit of the session."
Since you said you only track users who are logged in to your site, I imagine that is due to users who come to your site and still have to log in. The session metric is incremented when they hit your site. I guess after loging into their accounts they are redirected to a new page (which is when your custom reports starts to count), where the session is not counted again.
- User lands on the login page of your domain (session = 1)
- Users logs in and gets redirected (session = 0)
- User continues to navigate multiple pages (session = 0)
Only steps 2. and 3. are covered by your custom report, hence you have 0 sessions. On the other hand, users coming to your site that are still logged in will increment the session metric in your report.
This is what I can think of without any given other information. Adding the Unique Pageviews metric might help to narrow down your problem.