When it comes to this sort of gateways with the SX1301, it is a practice to the Ethernet interface’s MAC address to create an EUI-64 for the gateway EUI (or gateway ID). If you never had to set a value, it implies that the Gateway OS is aware of what to use for the EUI.
According to PiSupply’s documentation, the reset is indeed GPIO 22: https://github.com/PiSupply/IoTLoRaRange/tree/master/IoT%20Lora%20Gateway%20HAT
This is not really related to the RAK2247, but the HAT itself.
In the thread I linked to below, it appears that Chirpstack Gateway OS refers to the GPIO number as just “pin”, so 22 is probably correct.
Are you sure that the HAT and the RAK2247 are connected securely?
Something similar unfolded here: Unable to get Waveshare Gateway HAT working - #11 by Vilberg_Sindri