I also have the same problem , one of my pairs cannot update the GAM , is there any solution for this problem or how to investigate the issue since all my sensors are using the same proxy server and DNS server .
I need to Know the GAM update Links in order to add it all to the Proxy server Wight list.
The ems.log is accessed from the Manager, Manage > Troubleshooting > System Log,
You can use the Tail option to view the log in real time and see the error when you replicate the issue.
What Manager software version and Sensor model / software versions are you using?