@Sonotorian 

The red LED means they are connected, but it just has a slow connection due to where it is, look to move it to a different outlet as you want it to be green.

I would place all four in the same room first, then pair them up. Use the tpPLC utility to see if all four show connected. If not, use the utility to add them manually.

Here is a FAQ that shows how to add them: https://www.tp-link.com/us/support/faq/1059/

@Tony Thanks for the info. I'll try that, but when it was displaying the red light was when I was alluding to them being on the same circuit, 2' apart (same room).

@Sonotorian 

If they were that close then the wiring may either be bad or there is something else causing that much interference (ex. appliance) that the powerline adapter is showing the connection is slow. If you try a different set of powerline adapters and those show green, then the problem is likely the powerline adapter showing red itself.