Not able to use vSPoT API's

I'm not able to connect to vSPoT api's using mqtt broker. 

vSPoT instance IP -  192.168.99.135
mqtt broker IP -  192.168.99.122,
venue_id - vspot
password - 12345678

below is my mosquitto-bridge config file:

pid_file /tmp/mqtt_bridge.pidautosave_interval 0
autosave_on_changes false
persistence true
persistence_file mqtt_bridge.db
persistence_location /tmp/
log_dest file /tmp/mqtt_bridge.log
log_type debug
# listener for MQTT messages without PSK
listener 1883 192.168.99.122
connection spot_push_api_mqtt_bridge
address 192.168.99.135:8883
topic "1.0.0/LOC/SPOT_GPB/vspot/GPB_LOCR" in
bridge_tls_version tlsv1
bridge_identity vspot
bridge_psk 12345678

I've used the following command to start the local mosquitto broker:

mosquitto -c mosquitto_bridge.conf

After this I locally subscribe to the mqtt-bridged TLS PSK connection to venue server using the mosquitto_sub utility:

mosquitto_sub -h 192.168.99.122 -p 1883 -t "1.0.0/LOC/SPOT_GPB/vspot/GPB_LOCR"

I was expecting some encoded message streaming on my stdout. Unfortunately this is not happening. 

Help would be appreciated. Thanks!

PS: I'm using the instructions from - https://github.com/rksg/gpb_mqtt_sample_client