It could be that you're fatigued of a particular medium or genre. If it's novelty or originality you're after, some things will only work the first (and sometimes second and third) time they happen but not if they happen every time.
Or it could also be that your tastes have matured and you haven't realised it yet. I don't know if you're familiar with that feeling of re-watching an old movie or series you used to love as a kid and realising it's not as good as you remember; this could be that but in real time.
I hope you're able to find that spark you're looking for, but it might not be hidden in the same places you used to find it.