See "systemctl status apnscp.service" and "journalctl -xe" for details.
[root@instance-20220722-1816 ~]# journalctl -xe
-- The result is failed.
Jul 22 18:42:25 instance-20220722-1816 sshd[438836]: fatal: Privilege separation user sshd does not exist
Jul 22 18:42:51 instance-20220722-1816 sshd[438842]: fatal: Privilege separation user sshd does not exist
Jul 22 18:42:59 instance-20220722-1816 sshd[438843]: fatal: Privilege separation user sshd does not exist
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: apnscp.service: Found left-over process 426803 (redis-server) in control group while starting uni>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: This usually indicates unclean termination of a previous run, or service implementation deficienc>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: apnscp.service: Found left-over process 427091 (shellinaboxd) in control group while starting uni>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: This usually indicates unclean termination of a previous run, or service implementation deficienc>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: apnscp.service: Found left-over process 427092 (shellinaboxd) in control group while starting uni>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: This usually indicates unclean termination of a previous run, or service implementation deficienc>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: apnscp.service: Found left-over process 427093 (shellinaboxd) in control group while starting uni>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: This usually indicates unclean termination of a previous run, or service implementation deficienc>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: apnscp.service: Found left-over process 427094 (shellinaboxd) in control group while starting uni>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: This usually indicates unclean termination of a previous run, or service implementation deficienc>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: apnscp.service: Found left-over process 437524 (httpd) in control group while starting unit. Igno>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: This usually indicates unclean termination of a previous run, or service implementation deficienc>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: apnscp.service: Found left-over process 437527 (httpd) in control group while starting unit. Igno>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: This usually indicates unclean termination of a previous run, or service implementation deficienc>
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: Starting ApisCP backend service...
-- Subject: Unit apnscp.service has begun start-up
-- Defined-By: systemd
-- Support: https://access.redhat.com/support
--
-- Unit apnscp.service has begun starting up.
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: apnscp.service: Main process exited, code=exited, status=255/n/a
Jul 22 18:44:32 instance-20220722-1816 httpd[438884]: AH00543: httpd: bad user name nobody
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: apnscp.service: Failed with result 'exit-code'.
-- Subject: Unit failed
-- Defined-By: systemd
-- Support: https://access.redhat.com/support
--
-- The unit apnscp.service has entered the 'failed' state with result 'exit-code'.
Jul 22 18:44:32 instance-20220722-1816 systemd[1]: Failed to start ApisCP backend service.
-- Subject: Unit apnscp.service has failed
-- Defined-By: systemd
-- Support: https://access.redhat.com/support
--
-- Unit apnscp.service has failed.
--
-- The result is failed.