3.1. Some older request are not showing in Queue or Filters
In HelpSpot version 3.2.3 or greater, a setting was created to limit a filter or a My Queue to the past year of results. This was designed to improve poorly constructed filters and can be adjusted in Admin -> Settings -> System or disabled there if desired.
If you're seeing some tickets "disappear" after upgrading it's like due to this setting so you may want to extend the range to more days or disable.