If Grimgor Ironhide enters play in a zone with no development, and my opponent has in play Eatine Harbor, does Grimgor lose his ability?

Yes. Eatine Harbor is a constant effect that removes triggered effects. Grimgor's ability is a "Forced" effect, so it is removed by the Harbor before it can trigger.

Thank you, for the reply.

Another hope destroyed by the frickin HE support

Why not just, you know, first play a dev, then play Grimmy ? Unless you have Squig Pen in the zone you want Grimmy in, but then, that's your own fault .