By reference codes, you mean https://wolfgangklenk.wordpress.com/2018/10/12/espruino-on-rak8212-accessing-the-nb-iot-nb1-modem/ ?
What happens if you manually add each command on the left-hand side of the IDE one at a time? You can also add at.debug() to get debug text printed to help you.
The problem may be that you're executing the commands right after each other with no delay between them. In that case, it may be that the modem is just not having time to get a connection.
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