Modem Error with Custom Board

Question

Hi, 
 I've started incorporating our own custom board files into a project and have encountered a strange issue. The project build fine, but I cannot seem to communicate with the modem. 
 I get the following error when attempting to send an AT command: 
 lte_lc: nrf_modem_at_printf failed, reported error: -1 
 
 Apologies if this is a silly question, but what am I missing? Is there something in the device tree or overlay files that I have forgotten to add perhaps? 
 
 EDIT - Some more details: 
 In my prj.conf I have all the usual (this is a snip of my file, not the whole prj.conf) CONFIG_UART_INTERRUPT_DRIVEN=y
CONFIG_NETWORKING=y
CONFIG_NET_NATIVE=n
CONFIG_NET_SOCKETS_OFFLOAD=y
CONFIG_NET_SOCKETS=y
CONFIG_LTE_LINK_CONTROL=y
CONFIG_LTE_NETWORK_MODE_NBIOT_GPS=y

# Modem library
CONFIG_NRF_MODEM_LIB=y 
 
 Other than the board files, I also upgraded the SDK version that this app runs on from 2.2.0 to 2.4.2. When using 2.2.0 everything works perfectly. However the error persists when I change to 2.4.2. Is there something new I have to include or change to be able to use 2.4.2?

Rey · Accepted Answer

Answering my own question in the hopes that this helps someone else in future. 
 
 It seems that with the jump from SDK version 2.2.0 to 2.4.2 the modem lib now requires an init function to be called first: 
 nrf_modem_lib_init(); 
 This fixed the issue :)

Modem Error with Custom Board

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