Figuring out if there’s a proxy on the network

Hi, so I have some issues trying to figure out if there’s a current subscriber on the network utilizing a proxy/VPN.

However I’m unable to determine how to go about searching for that. We use an rXg, and Amazon Prime Video seems to think we’re acting on one - which is blocking users from viewing things. We contacted our ISP, and they distributed a new block of IP’s, and it worked - until it got blocked again.

I’m not sure sure if this a subscriber abuse, or an issue on AMZ’s side, or our ISP. I searched our entire network and nothing looks alarming.

Any ideas ? Tools I could use to check?

Thanks for any and all help!