I had a look too kelvinhall, I agree with gipetto. It looks like you've only connected your rows, haven't connected any columns and haven't connected any of your switches to your diodes. When I run DRC on your PCB, yes it shows 0 'Problems' but on the other tab it shows 60 Unconnected Items. Turning on the Ratsnest makes this really obvious.
Your edge cuts are fine if you want sharp corners. If you want curved corners, you have to use the 'Add graphic arc' tool when you have the Edge Cuts layer selected. For a simple rectangular board like yours, you'd need 4 straight lines and 4 90 dregree arcs. Each line segment is a separate 'object' and can be manipulated individually. You may have been tricked by the way 'Add graphic line' seems to draw connected lines.
Thanks bpiphany, that's more or less what I thought with the 10uf capacitor 'limit'. My board is appearing in USB and responding now. Currently I'm trying to figure out where I've gone wrong that's causing only the first 2 rows to function. I think I've probably missed a comma somewhere in TMK, but at least that's in the programming realm where I'm more comfortable. Thanks again to you and gipetto for assisting with the hardware diagnosis.