Check the service log:

sudo journalctl -u pho-collector -n 100 --no-pager

Run the collector interactively to expose configuration errors:

sudo -u pho-collector \
  /opt/particle_horizon/pho-collector \
  --config=/opt/particle_horizon/local_config/pho-collector/config.yaml

Verify that the service account can access the installation:

sudo -u pho-collector \
  test -x /opt/particle_horizon/pho-collector

Check runtime-directory ownership:

ls -ld \
  /opt/particle_horizon/local_data/pho-collector \
  /opt/particle_horizon/logs/pho-collector

These directories should normally be writable by pho-collector.

Inspect the stable symlink:

readlink -f /opt/particle_horizon/pho-collector

Build metadata for each installed version is available beneath:

/opt/particle_horizon/SOFTWARE/pho-collector-<version>-linux-<arch>/BUILD_INFO.txt

For example:

cat /opt/particle_horizon/SOFTWARE/pho-collector-*/BUILD_INFO.txt