In order for the "User Activity - Logins" dashboard to be populated an additional logger needs to be turned on for the TM1 service being analyzed.
Locate the tm1s-log.properties file. This is typically found in the following directory on the TM1 server - install_dir\samples\tm1\PlanSamp
Copy the tm1s-log.properties into your TM1 configuration directory (i.e. the directory where your tm1s.cfg file is)
Edit the file in notepad and add the highlighted entry after the one below:
Note: This may require a TM1 service restart if the file wasn’t present previously. More details are available here.
Once added you should see entries for login and logouts in the tm1server.log file and these should flow through into the Log File Search and Analysis dashboards once the package has been uploaded.