Dumbbell Handle Adjustment Troubleshoot
Turn both dumbbell adjustment knobs counter-clockwise to the lowest weight setting.
Examine the weight plates. Rotate any plates that have the selection tongue facing the dumbbell grip until the selection tongue faces away from the dumbbell grip.
Examine the selected position of the weight plates on either side of the dumbbell handle. Remove and reposition the weights if both sides aren't a mirror image of themselves.
Adjustment Knob Troubleshoot
Examine the dumbbell handle for proper alignment with the base. Depress the release switch on the dumbbell handle and fit it into the handle fully if it's not fitted properly.
Examine the orientation of each weight plate and rotate any plates that have the selection tongue facing the dumbbell grip until they face away from it. This is a solution if you're experiencing difficulty turning the adjustment knobs.
Remove the weight plates and examine the dumbbell base for any obstructing debris preventing the knobs from turning. Clear out the debris and replace the weights.