Wireless router problems

So my studio is in a log cabin at the end of the garden. I have a wired Ethernet port in the cabin served by:

Cable internet > Wireless Router > Repeater > LAN connection (30m under the lawn)

If I connect my laptop via an Ethernet cable to the port the internet works fine. But no matter what device I use I can’t get a wireless router to work with at the end of this chain with the exception of a Kingston G2 portable battery pack thing that I can’t spare specifically for this purpose. Is there any reason an Access Point device won’t work with this? I’m a bit clueless at this sort of thing. Here’s what I’ve tried today with no success (set as an AP):

Hope that all makes sense. Help!