First, go to https://metahuman.unrealengine.com/ and upgrade the MetaHuman you need to version UE5.5.
Then, re-download and re-import every MetaHuman you use in your project through Bridge — make sure none of them are from a different version.
The reason is that MetaHuman in version 5.5 use a different material system compared to previous versions. To use them properly, your entire MetaHuman setup in the project must be consistently updated to version 5.5.