Service 4wd light on

What is your question?

Service 4wd light came on and 4wd will not engage. Had been working just 2 days prior. Replaced Front Axle 4wd Shift Actuator Switch after researching (and it was only $79) but still does not work. Tried pulling #8 fuse and back seat fuse but no success. Indicator lights all blink when car is turned on then stops at 2wd. I think I hear a little vacuum sounding noise when I move switch from 2wd through other positions but they just blink with 2wd on constant. Hope someone can help. Thanks.