Need help regarding PSU

Today I upgraded my psu from a 450 watts psu to corsair rm550. But the plug(13A) doesn't fit in the UPS socket , so I used a connector( 6, 10 , 13A).
Now the problem is when I use a connector my UPS shows a reading of only 20 watts(even while gaming) , whereas my old psu used to draw 60-80 watts normally and 150 -170 watts while gaming. Then I used the cable from my old psu and the readings are again 60-80 and 150-170 watts.
So can anybody tell me why this could be happening and which one should i use(connector or old psu cable)? or is there anything else i should do?
thanks in advance.