Nexgard not working to kill flea eggs

I recently picked up fleas from a friend, apparently. Both of my cats are indoor only, and I have no carpet, only hardwood. As soon as I realized the problem, I took them to the vet to get treated and called pest control. I've had pest control out to my house twice now. I have vacuumed the bejesus out of my house and furniture. I have washed bedding, etc. I've probably read around 20-30 articles and blog posts about flea infestations and, short of giving my cats flea baths (which I will not do), I have done everything I can think of.

My question is this: I'm wondering why, after two treatments of Nexgard and two home pest control treatments, I'm still seeing flea eggs fall off my cat. I should clarify that it's not a week or two after their treatment--it's literally within the first couple of days.

I understand the flea life cycle is insanely long (hence, parasites), but I thought Nexgard is supposed to prevent fleas from laying eggs. Should I switch medicine? Anything other than Bravecto?