I realized that the passport service is stopped and when I try to start it with the command service passport start I got this in the console:

ubuntu@ip-172-31-2-157:~$ sudo service gluu-server-3.1.5 login
gluu-server-3.1.5 is running...
logging in...
root@ip-172-31-2-157:~# service passport start
Starting passport:
Checking logs for possible errors:
Some error encountered...
See log below:

2020-06-02T15:26:03.363Z [INFO]     Loggers reconfigured
2020-06-02T15:26:03.636Z [INFO]     getTokenEndpoint. Found endpoint at https://toid.tergar.org/oxauth/restv1/token
2020-06-02T15:26:03.701Z [INFO]     getRPT. RPT details were received
2020-06-02T15:26:03.758Z [INFO]     getConfiguration. Passport configs received
2020-06-02T15:26:03.759Z [INFO]     Configuration data has been parsed

For details please check /opt/gluu/node/passport/server/logs/passport-2020-06-02.log .

Stopping passport: OK

Exiting...

This is what the /opt/gluu/node/passport/server/logs/passport-2020-06-02.log file contains:

2020-06-02T15:26:03.363Z [INFO]     Loggers reconfigured
2020-06-02T15:26:03.636Z [INFO]     getTokenEndpoint. Found endpoint at https://toid.tergar.org/oxauth/restv1/token
2020-06-02T15:26:03.701Z [INFO]     getRPT. RPT details were received
2020-06-02T15:26:03.758Z [INFO]     getConfiguration. Passport configs received
2020-06-02T15:26:03.759Z [INFO]     Configuration data has been parsed