I've just installed Pi hole but uable to download any apps, the store works but no apps download.
I have the Windows 10 telemetry list enabled which seems to be the cause, disabling it fixes the issue.
Anyone have an idea what domain i need to whitelist from Windows 10 telemetry list?
But that's OK... Allow me to point you at the FAQ's section, where you will find the answer you are looking for.
haha I always get that 
I should have said the first thing i did was look at the FAQ, added those domians to my whitelist but no go. Turns out I also need to add www.msedge.net to the whitelist since that part of the Windows 10 telemetry block list.
Hopefully the FAQ can be updated for those that are using Windows 10 telemetry list but want a functional windows store.
Ah ok! Feel free to update that FAQ, it's in WIKI mode, so anyone can edit
Actually I must have missed something but adding www.msedge.net does nothing.
The store currently throws "Something went wrong on our end" error. Removing the telemetry list lets me download from the store. I guess I have some hunting to do to figure out which of the urls in the list is causing this issue, I have a possible of 147 urls when comparing to my old win10 telemetry list, that I have been using for months before moving to pihole.
Added displaycatalog.mp.microsoft.com to the whitelist than ran pihole -g and then pihole restartdns. Flushed the DNS on my computer then tried to download an app and this time it started to download.