Your assumption about pushing the pedal to the floor is correct, there should be a resistance point at the end of it.
I replied to your other post about how this works. Check with the car off and notice the resistance point at the end of the pedal when floored.
If you do not feel anything, then your kickdown switch has probably broken (my worst fear..! J/K). Not sure what involves replacement.
2006 E350 w/ 155k miles (Daily Driver)
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)