Vacuum pressure from blending is the likely cause. Do not force it.
- First: Ensure the blender is completely stopped and unplugged.
- Then: Gently twist the lid while lifting. Sometimes waiting a minute for pressure to equalize helps.
If that didn't work: You may have put the jar on the base incorrectly. The jar handle must face the control dial and align with the slot in the jar pad. An off-center jar can warp the lid seal. Remove the jar from the base first, then try twisting the lid again.
Prevention: Don't overfill. Max capacity is 56 oz (1.6 L). For hot blends, start on low speed as directed to minimize sudden pressure changes. Always let the blender stop fully before attempting to remove the lid.