Ok. Let me ask you this…
What kind of cable are you using to connect the microphone to your audio interface? Obviously, if you’re using a Shure SM57, one end of the cable is XLR. Is the OTHER end of the cable XLR as well? Or is it 1/4" TRS? Believe it or not, this makes a difference, as the Komplete Audio 6 interface actually only has true microphone level inputs on the XLR connectors of inputs 1 & 2. The setting of the “instrument / line” switch on the front makes no difference when an XLR connector is connected to the input. The XLR connections of inputs 1 and 2 are ALWAYS at mic level. That said, the TRS connections of inputs 1 and 2 are EITHER at line level, or at instrument level depending on the setting of the switch.
The thing is, line level is the highest impedance of the three, meaning you would be hard pressed to hear ANYTHING from a dynamic microphone plugged into a line level input. Instrument level is next on the list, lower impedance than line level, but higher than mic level, and in that case, you might hear something, but it may be too low a signal to be useful (especially with a dynamic mic). This sounds like what you might be experiencing… Mic level is the lowest impedance, and the one you want to use for you microphone. The only way to access a mic level input on the Komplete Audio 6, is to use an XLR connector connecting to the Komplete Audio 6. Assuming you CURRENTLY have a TRS connector, you can make it XLR by either getting a TRS to XLR adapter, or you can switch out the cable to a true XLR to XLR mic cable.
So to summarize, IF you are using a cable that has 1/4" TRS on the end opposite the microphone, then you are likely having a problem because of that–this is particularly true when using a DYNAMIC microphone (as the SM57 is) versus a condenser microphone. If, on the other hand, your cable IS ALREADY XLR to XLR, then I’ll try to bug you with more questions.
Now… that might not be your ONLY problem, but let’s start with that.
Just as a follow up question, are you able to see a signal on the LED meters on the interface itself when you plug your mic in and raise the gain on the input?