Looking at your error message (which I’ve edited to remove your public IP addresses), it says that Multiple NATs have been found. If you don’t have more than one router in your home network, then this issue is being caused by the network configuration of your ISP.
Your ISP will need to give you a public IP address (either static or dynamic) for ARC to work. Can you check with them whether they are doing this?
It is highly likely that your network provider is using Carrier-grade NAT. You can see that if you can compare your public IP with your WAN IP (on the info page of your router). If both don’t match, your ISP uses CGNAT and it’s probably why you won’t be able to use ARC as long as you don’t have a dedicated public IP. Looking at the error message, those two addresses are indeed different, so I suspect your ISP is using CGNAT.
You have my sincerest apologies for the delayed response here, we’ve been dealing with a higher-than-usual volume following our release and we’re working as quickly as we can to get back to everyone.
Following on what @Geoff_Coupe has mentioned, are you still running into issues here? If so, have you contacted your ISP to confirm you have a public IP address?