So in the current event when I summoned "Protector with Eyes of Blue" it won't let me use it's effects event if that's the first thing I do and I'm first. Also when I went first I couldn't special summon "Blue-Eyes Alternative White Dragon" and I had the first necessary card in my hand.
I had similar issues, I was using the skill Heavy Starter, and that doesn't allow special summons or effect activation on first turn
What's your current skill?
Certain skills such as Balance prevents you from using monster effects on your first turn.