VRChat用にアバターを変換したいができない

自作のモデルを、VRM Converter for VRChatを使いVRChat用に変換したいのですが、下記のエラーメッセージが出てきてできません。
自作のモデルは、blenderでVRM書き出し→unityで変換という流れです。
FBXで書き出ししてからUnityでVRMに変換→VRChat用に変換という流れでやってみてもできませんでした。
FBXからprefabファイルも作ってみたのですが、VRCSDK3のコントロールパネルに出てきません。
対処方法がわからず詰まってしまっています。わかる方がいればよろしくお願いいたします。

エラーメッセージ全文

ArgumentNullException: Value cannot be null. UniGLTF.UnityPath.FromAsset (UnityEngine.Object asset) (at Library/PackageCache/com.vrmc.gltf@0.99.2/Runtime/UniGLTF/IO/UnityPath.cs:350) Esperecyan.Unity.VRMConverterForVRChat.UI.Wizard.GetAssets Path (UnityEngine.GameObject vrm) (at Library/PackageCache/jp.pokemori.vrm-converter-f or-vrchat@38.0.0/Editor/UI/Wizard.cs:698) Esperecyan.Unity.VRMConverterForVRChat.UI.Wizard.OnWizardCreate () (at Library/PackageCache/jp.pokemori.vrm-converter-for-vrchat@38.0.0/Editor/U I/Wizard.cs:550) System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection. Binder binder, System.Object[] pa rameters, System.Globalization. CultureInfo culture) (at <eae584ce26bc40229c1b1aa476bfa589>:0) Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation. System.Reflection. MonoMethod.Invoke (System.Object obj, System.Reflection. Binding Flags invokeAttr, System.Reflection.Binder binder, System.Object[] pa rameters, System.Globalization.CultureInfo culture) (at <eae584ce26bc40229c1b1aa476bfa589>:0) System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <eae584ce26bc40229c1b1aa476bfa589>:0) UnityEditor.ScriptableWizard.OnGUI () (at <a259d3c004024353a2c217da97495055>:0) System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection. Binding Flags invokeAttr, System.Reflection. Binder binder, System.Object[] pa rameters, System.Globalization. CultureInfo culture) (at <eae584ce26bc40229c1b1aa476bfa589>:0) Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation. System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.Binding Flags invokeAttr, System.Reflection. Binder binder, System.Object[] pa rameters, System.Globalization.CultureInfo culture) (at <eae584ce26bc40229c1b1aa476bfa589>:0) System.Reflection.MethodBase. Invoke (System.Object obj, System.Object[] parameters) (at <eae584ce26bc40229c1b1aa476bfa589>:0) UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at <a259d3c004024353a2c217da97495055>:0) UnityEditor.HostView.Invoke (System.String methodName) (at <a259d3c004024353a2c217da97495055>:0) UnityEditor.HostView.OldOnGUI () (at <a259d3c004024353a2c217da97495055>:0) UnityEngine.UIElements.IMGUIContainer. DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 parentTransform, UnityEngine.Rect clippingRect, System. Boolean isComputing Layout, UnityEngine.Rect layoutSize, System.Action onGUIHandler, System.Boolean canAffectFocus) (at <b6a7e1825c0b45d3b072928 2e86cc687>:0) UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, UnityEngine.Matrix4x4 world Transform, UnityEngine.Rect clippingRect, S ystem.Action onGUIHandler, System.Boolean canAffectFocus) (at <b6a7e1825c0b45d3b0729282e86cc687>:0) UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Action onGUIHandler, System.Boolean canAffectFocus) (at <b6a 7e1825c0b45d3b0729282e86cc687>:0) UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Boolean canAffectFocus) (at <b6a7e1825c0b45d3b0729282e86 cc687>:0) UnityEngine.UIElements.IMGUIContainer.SendEventToIMGUI (UnityEngine.UIElements.EventBase evt, System.Boolean canAffectFocus) (at <b6a7e1825c0b 45d3b0729282e86cc687>:0) UnityEngine.UIElements.IMGUIContainer.HandleEvent (UnityEngine.UIElements.EventBase evt) (at <b6a7e1825c0b45d3b0729282e86cc687>:0) UnityEngine.UIElements.CallbackEventHandler.HandleEventAtTargetPhase (UnityEngine.UIElements.EventBase evt) (at <b6a7e1825c0b45d3b0729282e86c c687>:0) UnityEngine.UIElements. MouseCaptureDispatchingStrategy. Dispatch Event (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements. IPanel panel) ( at <b6a7e1825c0b45d3b0729282e86cc687>:0) UnityEngine.UIElements.EventDispatcher.Apply DispatchingStrategies (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel