Merging model parts causing FBXs not to export

I am having an issue with exporting low poly versions of my character NPCs for VR purposes in Unity. I create Actor Builds from the basic CC3+ model, compress the UV maps, but when I merge the body model parts and clothing in the Scene tab I cannot export an FBX from the model file. Has anyone else had this issue before, or have any ideas for troubleshooting?

Thank you!

Could you please record a video of your process? It’ll make it easier for others to replicate exactly. Thanks.

Of course thank you! Here are photos of my process:

  1. I Optimized and Decimated the model into an ActorBuild
    2)I went to the Material List and merged the UVs down

Don’t do that last merge body parts step. It does not gain you anything, since all parts of the character are already rigged to the skeleton.