Next step could be to turn on debug in config/passbolt.php file by adding:
return [
'debug' => 'true',
'App' => [
...
Website will say “Unsafe Mode” in footer on login page if debug is successfully enabled. You can comment it out when done using.
You’ll also want to make sure there is a “debug.log” file in the logs folder, writable by webserver user (on my Centos7 install it’s nginx).