Question about desecrates

Here is my issue.



Whit Ulaman omen + suffix omen i cannot desecrate this armor whit an ancient rib even tho i have a free suffix slot.

Got a message "Omen is incompatible whit this desecrating item".

I'm targeting the lightning and chaos suffixe wich ,according to PoE2DB should be available.

WXhat is going on plz?