You are correct to suspect that the multiroom box likely needs activation codes being re-sent.
There's two ways you can achieve this, depending on how urgently you want this resolving.
1: Call in - 150 from VM or 0345 4541111 otherwise, choose options for "I have a fault", press nothing else, just wait - and explain your fault to the agent. In other words, I'm missing channels from my second box.
2: Wait on this forum, staff should respond but it may take a few days.
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