If you have followed the guidance in our hierarchicalMenu widget documentation and Hierarchical facets documentation to ensure you hierarchical attribute is in the same format but one of your hierarchical levels is still not appearing theres a few things we recommend double checking.
First ensure that all levels of your hierarchical attribute are defined in attributesForFaceting using dot notation. Also ensure that you have included all levels of your hierarchical attribute in the hierarchicalMenu widgets attribute parameter.
If one of your levels is missing in your UI then double check you have the correct separator. By default the separator is " > ". This means you need to only have one space on each side of the separator in the attribute otherwise the level will not appear in the hierarchicalMenu widget.