I'm sorry that you're having trouble with the plugin. Could you please provide us with more detail so we can diagnose this issue?
What versions of Unreal and Cesium for Unreal are you using?
Where did you download the plugin from? The Unreal Marketplace, or Github?
Please describe step-by-step what you did leading up to the error. For example, did this happen after adding a 3D Tileset to your level? Did this happen after entering Play Mode?
UnrealEditor_CesiumRuntime!CesiumGeometry::Plane::Plane() UnrealEditor_CesiumRuntime!Cesium3DTilesSelection::createCullingVolume() UnrealEditor_CesiumRuntime!Cesium3DTilesSelection::ViewState::create() UnrealEditor_CesiumRuntime!ACesium3DTileset::CreateViewStateFromViewParameters() [E:\BEL Project\Visualizer\Plugins\CesiumForUnreal\Source\CesiumRuntime\Private\Cesium3DTileset.cpp:1630] UnrealEditor_CesiumRuntime!ACesium3DTileset::Tick() [E:\BEL Project\Visualizer\Plugins\CesiumForUnreal\Source\CesiumRuntime\Private\Cesium3DTileset.cpp:2082] UnrealEditor_Engine!AActor::TickActor() [D:\build++UE5\Sync\Engine\Source\Runtime\Engine\Private\Actor.cpp:1516] UnrealEditor_Engine!FActorTickFunction::ExecuteTick() [D:\build++UE5\Sync\Engine\Source\Runtime\Engine\Private\Actor.cpp:251] UnrealEditor_Engine!FTickFunctionTask::DoTask() [D:\build++UE5\Sync\Engine\Source\Runtime\Engine\Private\TickTaskManager.cpp:278] UnrealEditor_Engine!TGraphTask::ExecuteTask() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Async\TaskGraphInterfaces.h:1265]
UnrealEditor_Core!FNamedTaskThread::ProcessTasksNamedThread() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:758]
UnrealEditor_Core!FNamedTaskThread::ProcessTasksUntilQuit() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:649]
UnrealEditor_Core!FTaskGraphCompatibilityImplementation::WaitUntilTasksComplete() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:2125]
UnrealEditor_Engine!FTickTaskSequencer::ReleaseTickGroup() [D:\build++UE5\Sync\Engine\Source\Runtime\Engine\Private\TickTaskManager.cpp:556]
UnrealEditor_Engine!FTickTaskManager::RunTickGroup() [D:\build++UE5\Sync\Engine\Source\Runtime\Engine\Private\TickTaskManager.cpp:1583]
UnrealEditor_Engine!UWorld::Tick() [D:\build++UE5\Sync\Engine\Source\Runtime\Engine\Private\LevelTick.cpp:1626]
UnrealEditor_UnrealEd!UEditorEngine::Tick() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\EditorEngine.cpp:1924]
UnrealEditor_UnrealEd!UUnrealEdEngine::Tick() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\UnrealEdEngine.cpp:531]
UnrealEditor!FEngineLoop::Tick() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:5825]
UnrealEditor!GuardedMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:188]
UnrealEditor!GuardedMainWrapper() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:118]
UnrealEditor!LaunchWindowsStartup() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:258]
UnrealEditor!WinMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:298]
UnrealEditor!__scrt_common_main_seh() [D:\a_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]