I see what your problem is.
That's a 1.4 meter long, based-loaded, telescoping, end-fed vertical antenna.
It has significant losses on 40 meters.
Furthermore, all end-fed antennas require a good RF return, such as a resonant elevated radial or counterpoise. Since you don't mention that, that indicates to me that very little of your signal is actually ...
You might want to take a look at the HC_12 433Mhz devices, they have a range of 1Km. Cheap and dead easy to use. Build your test setup using these units, and iron out your bugs. Then move over to LoRa once you are comfortable that your system is functioning well. Then longer range will be possable.