I’ve had similar trouble with the LGT RF Nano — the radio part is a bit picky. What fixed it for me was lowering the data rate in the sketch and giving it a proper capacitor on VCC (even a small 4.7µF helped a lot). Also worth trying a different CE/CSN pin setup; these clones don’t always match the “standard” wiring perfectly. After that mine started talking to the gateway without any drama.