If you are only interconnecting coax cables with F81 barrel connectors, it shouldn’t cause a problem. Cable modems have a wide signal operating range.

Options: Ethernet cable or Moca or WiFi or powerline or pixie dust…

You can do a quick check of your rooms coax outlet by connecting the current modem/router to the other rooms wall outlet and see if it connects to the Internet. If not, then the coax to the room isn’t connected to the coax network. You’ll need to locate where the coax enters the building to find where the cables come together and connect them together with a splitter. This is where a Moca POE filter would be installed on the splitter’s input port.

Start simple.

Do you have a Moca POE filter… where is it installed?