DIAGNOSIS The air intake or exit port is blocked. The blower is a simple passive system channeling air from the motor fan; it doesn't have a separate switch.
FIX Clear the debris. Look for the dust blower outlet just above the shoe, near the blade. Use a small pin or compressed air to clear any packed sawdust from this hole. Also, check the intake vents near the battery port and trigger for blockage.
IF THAT DIDN'T WORK The internal air channel may be compromised. Disassemble the shoe/plunger assembly (requires torx bits) and check the plastic duct that directs air. It can crack or become misaligned.
HEADS UP The blower is weak by design, meant to clear fine dust. It won't blow away large chips. For a truly clear line, you still need an external vacuum connected to the dust port or a helper with an air hose.