Quick answer: Unreal Niagara emitter spawn rate set via Sequencer to non-zero showing zero in viewport? Sequencer evaluation order with VFX init - set the value before VFX activates.
Cinematic sequence sets VFX intensity = 5; cinematic plays; VFX shows zero intensity.
Set before activate
Sequencer track for VFX intensity precedes the activate track.
Or use System parameters
SetVariable on system parameters; applies independently of timing.
Verify in viewport
Sequencer scrub; VFX should respond. Mismatch = the order bug.
“Sequencer evaluation order is sometimes implicit. Make explicit.”
For cinematic VFX, the Sequencer track ordering is a checklist. Document.