Snap shot to ftp or localhost not working

HI there, I'm just trying to get snapshot to work, Ive tested on one of my sites and uploaded to the WPMUDEV space I have which works a treat no problem at all.

Although for another site ive tried to set it up to go to another location, firstly just to the webserver it was on, then to an ftp site. I set it up and test it and it connects successfully. but when I schedule or run a snapshot immediately nothing at all happens. no errors or pending messages,

the date of the next backup does appear but as far as I can tell nothing more occurs

nay help would be most appreciated

thanks