There is size limit for FBX export: https://support.capturingreality.com/hc/en-us/community/posts/4409049041042-FBX-Export-File-Size, you should simplify your model.
There is size limit for FBX export: https://support.capturingreality.com/hc/en-us/community/posts/4409049041042-FBX-Export-File-Size, you should simplify your model.