Power plug will not go inside the power socket!
Those don't look like tamper-resistant outlets to me.
New sockets are often just stiff.  That's how it is.
Mind you, the &quot;loosy goosey&quot; sockets you are accustomed to, are actually a fire hazard.  When contact is poor, a tiny gap will form, and electricity will simply jump across the gap.  This action is called &quot;arcing&quot; and makes a LOT of heat and soot, and that tends to make the arcing worse and worse, and it's a death spiral of destruction until you have a fire in the outlet.
So stiff outlets == good.  Plug it in totally square (in case it's a tamper-resistant) and push like you mean it.  Power plug blades are quite durable.  Honestly my biggest problem is breaking off ground pins from having pulled sideways on the cord.