I connect the condenser mic to line 1 or line 2 mic/line inputs but
do
not get any sound.
I can only get sound when using this an external phantom power supply.

You should at least get some sound. Neumann mics specifically "don't
work" at less than 48volts, but you get signal, just no headroom. I
suspect there is a wiring issue here, like an unbalanced cable in use.
I think those M-Audio boxes have Neutrik combo connectors, which should
be wired such that the TRS contacts DON'T carry Phantom power, even
though they're parallel with the XLR contacts. You're not using an XLR
-TRS cable on that mic are you?

Scott Fraser