systemctl custom service doesn't start on boot, but starts OK manually

Question

I have a Debian stretch on RPI. I need to start a custom service on boot up.

/lib/systemd/system/lora-packet-forwarder.service

Service is enabled, but shows up as inactive

lora-packet-forwarder.service - LoRa Packet Forwarder
   Loaded: loaded (/lib/systemd/system/lora-packet-forwarder.service; enabled; vendor preset: enabled)
   Active: inactive (dead)

Checking:

sudo journalctl -f -u lora-packet-forwarder.service 

-- shows up nothing

If I start it manually from console, it works fine:

sudo systemctl start lora-packet-forwarder.service

lora-packet-forwarder.service - LoRa Packet Forwarder
   Loaded: loaded (/lib/systemd/system/lora-packet-forwarder.service; enabled; vendor preset: enabled)
   Active: active (running) since Fri 2019-07-05 15:01:48 BST; 3s ago
  Process: 554 ExecStartPre=/home/pi/lora_gateway/reset_lgw.sh start (code=exited, status=0/SUCCESS)
 Main PID: 570 (lora_pkt_fwd)
   Memory: 568.0K
   CGroup: /system.slice/lora-packet-forwarder.service
           └─570 /home/pi/packet_forwarder/lora_pkt_fwd/lora_pkt_fwd

Jul 05 15:01:47 raspberrypi systemd[1]: Starting LoRa Packet Forwarder...
Jul 05 15:01:47 raspberrypi reset_lgw.sh[554]: Accessing concentrator reset pin through GPIO25...
Jul 05 15:01:48 raspberrypi systemd[1]: Started LoRa Packet Forwarder.

Here are the contents of the service file:

[Unit]
Description=LoRa Packet Forwarder

[Service]
WorkingDirectory=/home/pi/packet_forwarder/lora_pkt_fwd
ExecStartPre=/home/pi/packet_forwarder/lora_pkt_fwd/reset_lgw.sh start
ExecStart=/home/pi/packet_forwarder/lora_pkt_fwd/lora_pkt_fwd


[Install]
WantedBy=multi-user.target

I have a small shell script to reset the GPIO pin, before the lora_pkt_fwd is launched. Here are the permissions for both files:

-rwxr-xr-x 1 pi pi  1485 Jul  3 21:38 reset_lgw.sh
-rwxr-xr-x 1 pi pi 144680 Jul  3 20:17 lora_pkt_fwd

Regarding the settings, have tried already:

1. put "bash" for shell script - ExecStartPre=bash /home/pi/packet_forwarder/lora_pkt_fwd/reset_lgw.sh start
2. Tried combinations of After=network.target, Before=network-online.target, Wants=network-online.target in [Unit] section
3. Tried Type=simple and forking in [Service] section
4. Tries disable/enable the service and daemon-reload (just in case)

I could get this done with cron task or something , but I want to do it right.

Answer 1

Anyone looking here for the correct file, here is mine working.

[Unit]  
Description=Packet forwarder for LORA-Helium  
After=network.target  
StartLimitIntervalSec=0  

[Service]  
Type=simple  
Restart=always  
RestartSec=1  
StartLimitAction=reboot  
User=pi  
WorkingDirectory=/home/pi/sx1302_hal/packet_forwarder/  
ExecStartPre=bash /home/pi/sx1302_hal/packet_forwarder/reset_lgw.sh start  
ExecStart=/home/pi/sx1302_hal/packet_forwarder/lora_pkt_fwd -c  /home/pi/sx1302_hal/packet_forwarder/global_conf.json  

[Install]  
WantedBy=multi-user.target