Hi @frapell,
does the network id (MY_RFM69_NETWORKID) used on the node and the gateway match? Also other communication parameters like MY_RFM69_MODEM_CONFIGURATION, for example.
If, for example, your node has the following parameters...
#define MY_RFM69_NETWORKID 123
#define MY_RFM69_MODEM_CONFIGURATION RFM69_FSK_BR55_5_FD50
... you should pass the same parameters to the configure statement:
--extra-cxxflags="-DMY_RFM69_NETWORKID=\(123\) -DMY_RFM69_MODEM_CONFIGURATION=RFM69_FSK_BR55_5_FD50"
Also check if encryption settings match, if encryption is enabled.