If “transmissions” refers to sending data, then unless it’s really only sending a few times a year, an OTAA node should not activate itself for each transmission; that’s just a waste of air time. If your node cannot save its state between transmissions then ABP might be a better fit, along with the decreased security of disabling the frame counter checks. But going into a low power mode that preserves the activation details is much preferred.
As for OTAA: many more debugging steps and background in OTAA ok, 12h later I get denied, reboot gateway –> OK again …!? (Yes, that’s a long topic…)