I disconnected my front drive shaft from the differential to replace my neutral safety switch. I got that done and I am trying to put the u-joint back on. I am trying to turn the drive shaft and the front diff yolk and neither will turn. It is in 2WD and the light on the 4 button selector has 2HI lit up. Does this mean that I am stuck in 4WD? The front diff was spinning freely, but I put it in 4WD and took it back out and now that is also not spinning. I moved the blazer back and forth on the driveway and the driveshaft did change position. Thanks in advance for any help.

2000 Blazer 4 door, 4WD, 4 button 4WD.