DIAGNOSIS The blade assembly is designed to be removable but can seize from dried food or over-tightening.
FIX Hold the metal blending arm firmly. Grip the serrated plastic ring at the very base of the blade assembly (just above the blades). Twist the plastic ring counterclockwise. It may require significant force. Do not twist the metal shaft.
IF THAT DIDN'T WORK Soak the bottom 2 inches of the assembled blending arm in warm, soapy water for 10-15 minutes to loosen residue. Try twisting again with a dry rubber glove for grip.
HEADS UP The blade is extremely sharp. Never try to pry it off or use tools that could slip. If it's truly fused, consider ordering a new blending arm assembly rather than risking injury.