Obliterate!!! Blaze !!!

[wind crag]

Opponents turn: Opponent has Rokket Tracer on field. I have The Unstoppable Exodia Incarnate on my field, during the end phase I activate its effect to set Obliterate!!! Blaze!!! from my deck.

My turn: I activate the set Blaze targeting my Exodia Incarnate. In main phase I attempt to activate the Blaze ability through Exodia Incarnate but don’t see an “Activate” option.

I use my Wedju Temple to set 2 monsters then summon Snake-Eyes Doomed Dragon, putting my opponents monster in their backrow.

I check again and am now able to activate the Blaze effect through Exodia Incarnate.

What was stopping me from activating the effect in the first place? (Video attached for reference)

[sinful ingot]

There needs to be cards in the spell or trap zones to destroy in the first place. At the start of the main phase there weren't any. The field zones isn't one of the spell and trap zones

[wind crag]

Would cards in my spell/trap zones count to that (the Milennium monsters) or does it have to be in my opponents spell/trap zones