Hi @Phillip_Bird,
Who is your internet service provider?
@Robert_F is correct in that this particular diagnostic usually indicates a port conflict. However, in rare cases, this diagnostic message can also result from your service provider’s implementation of carrier-grade network address translation (CG-NAT). Here’s an example from another user: ARC and Telstra Smart Modem Gen 2
Since changing the port didn’t work, I recommend reaching out to your provider directly and inquiring about what options are available for port forwarding. You might ask if they have external IP addresses they can dedicate to your account.