Hi @Carey_Head,
Welcome in the community, a fellow community member here.
The reason Arc isn’t working, is that you have multiple layers of NAT translation.
Just to be sure, is your gear attached on the Orbi? If so, i would suggest you check if your Netgear C3700 can set in bridge mode.
Take a look at below post, here you see how to set your Netgear C3700 can be set in bridge mode
Kind regards,
Maarten.