Uploading FBX file

I have a blend model and have successfully uploaded as a obj file to mixamo. I would now like the colored version but can't seem to get an fbx file to upload. I have made sure that the copy and embedded textures are clicked but the file can't be uploaded. I'm assuming the file is to big or there is an other issue with how it's set up in blender but I dont have a good understanding of blender so am struggling to find an answer I can understand . Any advice is appreciated.