Suspense doesn’t mean danger, though it can, but more a case of the reader wanting to know what happens next.
Questions and possibilities, decisions and indecisions on the part of the characters, if you’d like to look at it this way.
What the “suspense” is depends on the type of story being written.
In a mystery this is obviously Whodunit, How did they do it, How can the detective prove they did it, Why did they do it.
In an action-adventure it’s a case of staying ahead of whatever danger threatens as well as possibly finding a treasure, rescuing someone, etc.
In a romance it is how will the couple overcome whatever is keeping them apart (as there has to be something doing that or you don’t have a story), when will they find their compromise or get over the problem, even will they or won’t they hit the mattress within these pages.
With fantasy you could have a bit of any of the above things going on simply taking place in a pseudo medieval world, on a different planet or dimension, in an altered historical landscape or in the future.
As the NANO month begins rushing down to the finish line, the suspense should be building at a quicker rate, too. You're past the middle of the book now (should end today with 28339 words or more), It's time to up the suspense ante for your readers!