Root Block

The root node block type of a NIF for object models should typically be a BSFadeNode.

A NiNode root node block might cause the model to be invisible in the game.

Dynamically enabling models with a root node block type other than BSFadeNode, BSLeafAnimNode or BSTreeNode causes CTD, hence the NIF is ignored for dynamic LOD.

A NiNode root node block type can be converted or changed with NifSkope. Right click the [0] NiNode, select Block, Convert, Bethesda, BSFadeNode, then save the updated NIF.

Otherwise use NifSkope to create a new BSFadeNode root node and then move everything into it as children using right click Copy Branch/Paste Branch and then Remove Branch, then save the updated NIF.

Certain types of models like grasses for example may be reported (vanilla grass models use BSFadeNode, so well made mods should follow that convention as well) but are never used for dynamic LOD anyways.