UnitiLite "cant find server (NAS drive)" often !

First post so here goes -

I have a Uniti Lite unit picking up files from a Western Digital NAS Drive.

I use Sky broadband with their standard router.

Often when i use the App on my ipad/phone the twonky server will not show on the screen however my laptop does.

Where do you think the fault lies (i.e NAS/Router/Unit) and would replacing the router with a better one improve this.

p.s The Uniti Lite is connected to the router now by cable !

Thanks for any help in this matter,

Bailster.