TL;DR
Assessment planning dates can temporarily hide qualifying future assessments from students and parents while staff coordinate deadlines.
Steps
Open General in Insights and edit Assessment Planning with administrator access.
Review the visibility cutoff for each relevant grade level.
Set a date that leaves students sufficient preparation time.
Save and check a qualifying assessment on each side of the cutoff.
Review the cutoffs regularly as the year advances.
This is separate from a task's announcement date and publication state. A task can exist for teachers while remaining hidden from students. If work seems missing, check all three controls before recreating it.
Related help
Publish assignments with useful timelines · Find missing tasks and restore completed or deleted work