Gonna throw out another solution here after flailing with this issue for few hours (thank you UE4). I’m overriding Tick in my class AAntiGravityTriggerBox which is derived from ATriggerBox, and my object is nested underneath another Basic Cube Actor object in my scene (nested via the Editor, not via my C++ code). I never figured out what, but after object construction and before my BeginPlay is called, something sets various tick flags back off (for example bCanEverTick amongst others, so good luck setting them in the constructor as documentation suggests). Based on the current AActor::RegisterActorTickFunctions implementation, I was able to register my Tick function by adding the following to the top of my BeginPlay override:
void AAntiGravityTriggerBox::BeginPlay()
{
Super::BeginPlay();
PrimaryActorTick.Target = this;
PrimaryActorTick.bCanEverTick = true;
PrimaryActorTick.SetTickFunctionEnable(true);
PrimaryActorTick.RegisterTickFunction(GetLevel());
...
}