I've had the same problem at times. Resetsim on the ones that immediately cancel your invites, sometimes that sorts them out. Story Progression will continue moving people in, though I have at times felt like it wasn't doing so fast enough. Make sure to send your Sims out to Gyms, art galleries, bars, parks, etc to scan for local talent that's recently moved in to town, if no one is there, just move on, they probably won't show up later either. Having a doctor has been really handy for meeting people, since a medical clinic pulls people onto the lot constantly. It's how I found both my gen 4 and gen 5 wives.
I hope your ghost town gets more lively soon, if you have Plasma 501, check the basement, that elevator is notorious for breaking and hiding tons of Sims where you wouldn't normally check.