Md5 is a method to hash every single file.
en.wikipedia.org
It means if 5 users upload the same file and one of them will be reported to be blocked by hash, then all of the files will be blocked too, even if owner, title and so on, are different.
In your case it probably means, that this file was reported to be blocked by hash. If it's your own original video, then maybe because of content that is violating some hosting rules... I dunno.
I don't think that md5 can be the same in 2 different files, but maybe?
You can try to reupload it, but I think you will get an upload error. Then last option is to reencode file. that will change md5 checksum for sure. You can also try to archive it to rar or zip.