Dead yeast?

Pardon my ignorance, I’m new to this. I added some yeast to my brew on thursday night and closed the lid on my primary fermenter. It’s now been 48 hours and I still haven’t seen any activity on my airlock. Is it possible that my yeast was bad? Can I just add more if that is it the case?

Likely it fine.

It’s possible that the lid is not completely sealed. So CO2 is escaping with out going through the air lock. Not a big deal.

Waite 72hrs, if no air lock activity, open the lid to see if a Krausen has formed.

What yeast? What’s the wort temp?