Also, I just did a sanity check on my previous suggestion... the test:
Went to init patch and tweaked amp envelope amount with velocity on to get a very noticable volume velocity range, tapped in some notes in so softly it was dead silence, and others firmly so they were well audible. Playing back the sequence, some notes were quiet and others loud with velocity toggled on, but with Amp velocity toggled off the played notes were all the same volume as expected. Velocity Response was set to 0 for this test.
If yours isn't doing same for this test I'd suggest contacting Sequential Support.