Registering Player Character with UCrowdManager

Try this:
a) Create your own class - child of ICrowdAgentInterface. For example:

UCLASS(BlueprintType)
class UCharacterCrowdAgentInterface: public UActorComponent, public ICrowdAgentInterface
{
	GENERATED_UCLASS_BODY()

	virtual FVector GetCrowdAgentLocation() const override;
	virtual FVector GetCrowdAgentVelocity() const override;
	virtual void GetCrowdAgentCollisions(float& CylinderRadius, float& CylinderHalfHeight) const override;
	virtual float GetCrowdAgentMaxSpeed() const override;
	virtual int32 GetCrowdAgentAvoidanceGroup() const override;
	virtual int32 GetCrowdAgentGroupsToAvoid() const override;
	virtual int32 GetCrowdAgentGroupsToIgnore() const override;
public:
	virtual void InitializeComponent();
};

b) Overide this functions(can see UCrowdFollowingComponent ) + register it in Crowd Manager:

void UCharacterCrowdAgentInterface::InitializeComponent()
{
	Super::InitializeComponent();
	UCrowdManager* CrowdManager = UCrowdManager::GetCurrent(this);
	if (CrowdManager)
	{
		ICrowdAgentInterface* IAgent = Cast<ICrowdAgentInterface>(this);
		CrowdManager->RegisterAgent(IAgent);
	}
}

c) Add it like component to your pawn (or character) (can do this in constructor of pawn class)