@terziyski

Thanlk you for the reply. I had done that on several occassions. 

I think I may have traced it back to the PoE injector which I received with the TP link router when I purchased it. 

I have a separate PoE splitter which I used to spilt the Ethernet and power for the router (ie testing if it maybe be the router’s internal splitter) but it is giving the same fault. If I power it using the 9V adapter it works perfectly. 

I'm powering it via a DC-ups which has a 9V selector. If I power the router directly from the UPS it works perfectly. I did that last night when I could connect to the router via cable to do a Quick Setup as AP. If I use the 9V power supply it works perfectly as well. I prefer to use PoE as I am powering another router as well, and have the cables pre-installed in my house. My country also has severe power system issues so want equipment running consistently and not having power spikes. I plugged the routers AC/DC 9V supply into the router and it works perfectly and I have also used the AC/DC 9V supply as the power source for the PoE (i.e. checking if the DC ups is faulty) and it worked and I was able to connect to the SSID, BUT, as soon as I went back to see if I could get the DC ups to work, it did not, and now neither does the AC/DC 9V supply via PoE. I am currently using the AC/DC 9V supply directly to the router and it works. This is not the preferred power setup for reasons described above.

I'll test a new PoE injector.