In some cases, instead of the admin interface, a white page with “502 Error” is displayed
In this case, you need to open the server console and check the following:
The DBMS is running.
sudo service postgresql status
if the service is not running, you should restart it
sudo service postgresql restart
If it still doesn’t help, then most likely we have a problem with the database. The problems may vary, but the most likely one is the disk overload.
Restart staffcop service
sudo service staffcop restart