You're fine as long as the grass seed was viable. It can take a while for it to germinate. I would give it a few more days.

Thanks, still not seeing anything pop. I used premium lesco sun and shade from home depot.

As tree_oracle pointed out, you're probably okay so long as the seed is viable (i.e., wasn't too old to germinate). The ground doesn't normally freeze in this part of New England for several more weeks. Air temperature probably doesn't have as significant an impact on seed germination as amount of available moisture & hours of daylight.

IMO it is not too late at all, especially near the coast. At my previous house, one time I sowed grass seed much later in the season than early October, and it was zone 5! I remember seeing the first grass seedlings pop up over Christmas vacation - believe it or not. Apparently it was a mild fall that year, and it has been a mild fall this year too.

I was just recently thinking about overseeding the little side yard with some clover, where I've started a lawn this year. Well it's not fully established yet - IMO establishing a healthy organic lawn is a multi-year process, because it takes a few years for perennials grasses to mature (kinda like growing perennials from seed). And I just top dressed this side yard with compost the past few weeks, and so I'll probably wait until spring to overseed.