I have 2 UPS of the exact same model. In one UPS, all of my Type B Plugs would not fit
In the first image, the hole on the socket is on the edge. My Type B Plugs (3 pin) would not fit. On the second image, the hole on the socket is on the middle and my Type B Plugs (3 pin) would fit. For reference, the last image shows what a Type B Plug looks like.
Edit: As it might be a "Fake" I included the picture of the serial number of the back of each UPS.
The first image shown is the UPS' serial with the plug that fits. The second image shown is the UPS' serial where the plug does not fit.