The group name is misspelled in pbm-agent.init , notice below:

The group should be mongod. This prevents the startup process from creating the pid folder and not be populated with the correct pid and the agent hangs trying to start. The link to the affected file can be found below:

The work around for this is to correct the group name, however, the init file does not progress as it fails to obtain the pid (I was not able to determine why as of yet), so we have to populate the pid file manually with the pid of the pbm agent process. Once we populate the file the service finishes it startup process and pbm agent continues to run without issues.

As a permanent fix I did the following and this has resolved the issue:

1. stop the pbm-agent service

2. remove the init file: sudo rm /etc/rc.d/init.d/pbm-agent

3. create the file  /etc/systemd/system/pbm-agent.service with the contents from here

4. chmod +x the above file

5. Enable the service: systemctl enable pbm-agent.service

6. Start the pbm agent: systemctl start pbm-agent

7. Check the status: