I get the same here - !rotation works fine, and detects maps in the maplist, but !maplist returns an empty line too:
<EggBot> !maplist
<DSBot> The following maps are installed:
<DSBot>
This causes !setnextmap to not work either:
<Egg098> !rotation
<DSBot> Host: The map rotation includes:
<DSBot> Host: [C&C_Complex.mix] C&C_Volcano.mix C&C_Canyon.mix C&C_Walls_Flying.mix
<Egg098> !setnextmap canyon
<DSBot> Host: [BR] ERROR: canyon not found.
I tried with my firewall turned on/off - same result for both