I've attached a 2TB external hdd to a Spark supplied huawei 630b router, and ticked the option to access the drive via a Samba share.

Can see it fine when access it, and it has about 6 directories, of various video files.  The 'TV' directory and the kids directories are fine, but the movies directory shows as empty.  When it is attached direct to a computer all files are present..

Have a bit of searching but all the responses are about linux, not really relevent to a locked down router.