What happens if you connect the first powerline to your switch and the second to the TV, do the other wired devices “disconnect” again? Is the TV also set up to use wifi as well (and if it is can you “forget” all wifi network/settings to ensure only the ethernet connections will be used)?
It varies, but usually you need to use port 5 on the switch to connect to your router. Use ports 1 through 4 & it can instantly drop all other connections. My 5 port Netgear does this.
Double check your switch is connected to the router from port 5 .