Hecatomb? Does it not slot in Knockout Blow from SS?

[Sapphire Lotus]

So Ive planned out a build in Pines, Knockout Blow states that it allows Melee Damage sets.

 

I purchased 5 Hecatomb's which are clearly labeled Melee Damage, I do not have Hecatombs anywhere else in the build, when I go to drag and drop, nothing lights up. None of my powers will allow it to slot, not punch, not Haymaker, not Knockout blow.

 

I am wondering if my character is required to actually be 50, I have enough experience for 50, just havent finished leveling him up completely due to having to swap sides for Power Pools. Does his power selection and slots need to be finished out to 50 fully to be able to slot purples?

 

I have the rest of my level 50 enhancements (Yellow/Orange) sets slotted.

[Adeon Hawkwood]

You need to be actually leveled up to 50 in order to slot purple sets. Other level 50 IOs can be slotted at level 47 but purples are special.