The non-standard function mlme_rx_enable declared in the header mac_mlme_rx_enable.h does not seem to be defined in 802_15_4_lib_gcc.a.
The compilers throws an error: undefined reference to `mlme_rx_enable' and searching for the symbol using with strings and grepping for mlme_rx_enable on the compiled library yields:
mlme_rx_enable_req
mac_mlme_rx_enable.o/
mac_mlme_rx_enable.c
mac_mlme_rx_enable.c
mlme_rx_enable_req
.rel.text.mlme_rx_enable_req
.rodata.mlme_rx_enable_req.str1.1
i.e. there seem to be no mlme_rx_enable function in the compiled library.
SDK version: nRF52 SDK 17.1.0
Best Regards, Andreas