This is interesting, @Tony. Thank you for the information, it would seem the problem is the same. In fact, the Pygate also responds with:
[567803149] lorapf: ERROR [down] Packet REJECTED, unsupported RF power for TX - 28
However, at the moment I do not know how to modify the packet forwarder on the Pygate, would possibly need to modify the firmware, but Pycom has not yet made this public.
Thank you again for your insight!