Unable to upload folders if they have subfolders in them without returning error msg

I am trying to upload folders which have many layers of subfolders in them.

 

When I try to click on the top level folder with its accompanying subfolders, I get an error message that such and such number of files can not be uploaded because they are not supported by Dropbox, even though the file types are common like pdf and txt.

 

If, however, I click down to the bottom most level where it is just a folder with files in them, I am either able to upload the one folder or sometimes I even have to manually select the files within the folder to get them to upload (and receive no error messages about unsupported file types).

 

With the massive amount of folders I need to upload, it will take days to upload at the one folder at a time level.

 

Can anyone tell me why I can not just click on the top level folder and get all of its subfolders to copy at once? Or at the very least, not have to go down to the single folder level?

 

I am using Chrome