I surely hope what I say is not the case, but...., here goes.
Many, if not all, vacuums made today can plug up with dirt internally, requiring you take to whole machine apart and clean it all out.
I often find new or nearly new ones discarded just because no one know how to, or even wants to, completely clean them.
Usually, this is a job for a "mechanically-minded person:", as it requires several tools and previous practice.
God bless your efforts.