Where are you looking (continent or country?).
Two possibilities:
1 - You're in the U.S. but are entering positive longitude, rather than negative (look for a warning message about eastern hemisphere).
2 - You're outside the U.S. and need to select the "Landsat" tileset by hitting the "L" key or choosing Landsat in the upper right tileset dropdown. Topo maps are not supported for areas outside the US.
