I’m trying to add a new imagery layer (Landsat 8) found here: http://wiki.openstreetmap.org/wiki/2014_West_Africa_Ebola_Response#Landsat. I go on Imagery Preferences>add TMS and the past the URL for Landsat 8 into the 1st box and then the 3rd box. I give the layer a name and have tried both giving and not giving it a max zoom, and then click OK. When I select the imagery layer nothing happens except red writing appears telling me there is a ‘500 error’. Ive tried adding other imagery layers on that list with the same problem. What am I doing wrong?