Can't infuse accessories or amulet?
That was made very clear before the patch launched. The only changes to infusions were for the “<item> (infused)” gear. And those are limited to rings and back pieces.
The innate +5 AR that they originally came with was replaced with an “Agony Infusion Slot”. That is the only slot that you can put the new infusions in.
If you want to infuse your accessories or amulets you need to spend 75 fractal relics to get the +5 AR versatile infusion.