That almost certainly means the firewall on the primary is blocking port 30568 or the primary has an ARM processor or very old AMD/Intel 64 bit processor.
Oh no, so the cause is the firewall port blocked, as I wasn't able to send audio to my primary because of the port blocked (message saying that the port 30567 is blocked).
And it's not possible for me to create an allow rule, as my primary is my work computer and firewall settings are all GPO based.
Is there any chance to change the incoming port to the secondary (my personal laptop, so I can open the port from there) to circumvent this?
Anyway, thanks for the help!